Depending on your viewpoint, the litany of sub par multiplayer experiences can be attributed to a rampant (and desperate) desire to pull more money from a product; the hope that an IP will continue to stay relevant (or appease a loyal fan base); or simply because it’s a legacy practice to cover as many bases as possible.
It doesn’t do the world or its characters any favours to reduce the elegance of its creation into a rampant ‘kill-a-thon’.
Any discussion about multiplayer will inevitably lead to the Call of Duty series, and why not? As an IP, Activision has had an absolute field day, not only with the amount of revenue streaming in from its various iterations, but the large and seemingly immovable fan base that follows it. No one would argue that Call of Duty’s success lies in its carefully refined multiplayer component (ironically, some call the single-player mode ‘tacked-on’). Unfortunately, the immediate train of thought for many developers is that multiplayer equals revenue, but this is far from the reality. At the most simplest review of that statement, it requires the word ‘great’ at the start. The reason why Call of Duty pulls in the crowd is not because it’s merely there: it’s because of the immaculate attention to detail that has been injected into each version. It’s an attribute that is virtually impossible to replicate on a first release: it requires time and constant modification in order to flourish as a commendable experience.
In terms of extending the value of the IP itself, multiplayer could have that effect. Left 4 Dead’s strength comes in the fact that multiplayer perfectly encapsulates what a potential zombie apocalypse could be like. The sense of discovery coupled with a balanced implementation of teamwork propels the game beyond a typical, scripted experience (incidentally, the single-player mode in Left 4 Dead is undoubtedly more unappealing). Unfortunately, the reverse is not true: a highly polished, scripted, single-player experience loses all sense of poise and grace once the mayhem of multiplayer is introduced. BioShock 2 and Dead Space 2 are prime examples of how a tight, well-paced singleplayer mode simply doesn’t translate. It doesn’t do the world or its characters any favours to reduce the elegance of its creation into a rampant ‘kill-a-thon’.
Unfortunately, the immediate train of thought for many developers is that multiplayer equals revenue, but this is far from the reality.
However, the main branch of this argument boils down to legacy. During the days of the 16-bit consoles and their subsequent replacements, multiplayer was a selling point of the unit itself. In fact, a lot of Nintendo’s marketing banked on the fact that the Nintendo 64 had four controller ports by default. It prompted a strong push to incorporate multiplayer into as many titles as possible, and it surprisingly paid off for a fair number of games. As a concept, multiplayer was far simpler in those times than it is now. Online gameplay was the domain of high-end computers, leaving the multiplayer to mainly be experienced with a group of people physically around one TV. Exploits briefly gave advantages to players who found them first, upon which they were imitated until they became standard practice. This simplicity, and the lack of any method to fix problems, gave a lot of free reign to developers.
That time has passed. We are now in an age where games are frequently multiplayer only, and are as elegantly thought out as the best AAA single-player title. Until all developers realise this, basic multiplayer additions to their single-player games will continue to fail.
Tacked-on multiplayer is the horrible habit that publishers picked up recently of throwing multiplayer elements into sequels of well-selling single-player games. Good examples include games like Bioshock 2, Dead Space 2, Grand Theft Auto 4, Uncharted 2 and 3, Assassin’s Creed: Revelations, and unreleased titles like Mass Effect 3 and Max Payne 3.
To be completely fair, sometimes the multiplayer is quite good, and ends up being a very fun multiplayer game in its own right. I would say that the Uncharted multiplayer was definitely fun for me, and people probably found the multiplayer in several of the other games to be quite enjoyable as well.
The issue that I have is when the multiplayer is half-baked, unwanted, broken, or otherwise faulty. It’s obvious that the publisher just wants to tick a box on the back of their game packaging, and they end up with a useless multiplayer component that nobody ever wanted. The problem is that the developer has wasted time and money on a useless multiplayer component, when they could have just spent that time on improving the single player game.
Even if the publisher hired a separate group of developers for the multiplayer (so they don’t interrupt the main single player development), the money needed to do that doesn’t come out of nowhere. It’s obvious that the publishers expect that the money spent on developing the multiplayer will be made back, and then some. Maybe they can charge an extra ten bucks at retail, or hold back some game content to use as paid DLC later? Maybe they expect to sell more units, because people will see the "includes multiplayer" label and buy the game based on that?
Any way you play it, the consumer loses. They end up paying more for a game with a multiplayer element that does not meet the standards of modern multiplayer games, which put a lot of time and effort into developing a perfect multiplayer experience. Somebody who wants a multiplayer game is far better off buying a game made specifically for multiplayer, or at least one where the developer actually cared about making the multiplayer actually good.
Let’s flip the argument over and look at another bad publisher habit: tacked-on single-player. This is exactly what you’d expect – multiplayer-focused games that make a short, unfulfilling, on-the-rails single player campaign just so they can say that the game has single-player. These are your 5-hour "junk food" campaigns of Battlefield 3 and Modern Warfare 2 and 3. I haven’t played any other recent games with tacked-on single player, but I wouldn’t be surprised if it’s also present in the more recent Halo games, Killzone 3, and other multiplayer-focused games.
I won’t go on about it anymore, but I want to finish with this: Publishers and developers should aim for the highest possible quality in every element of their games. For example, look at a Gears of War 3. It has a fully-fledged single-player campaign, as well as a well-rounded and polished multiplayer component. If publishers cannot take the time and effort to make a good multiplayer or single-player experience, they shouldn’t do it. They’re wasting their own money, which as a result, wastes the consumer’s money. If you cannot put 100% into both elements, they should ditch one and use the spare resources to make the other into a better game.