Though there can be many answers to that question, perhaps the simplest answer is escapism.

No matter whats occurring in your life many people enjoy the ability to escape to somewhere else for a few minutes or an hour or two and just forget about real life for a bit.  Whether its scoring the winning goal in a football game or racing in an F1 car, shooting terrorists in a FPS or defending the realm against an evil wizard, that ability to skip to someone else is a compelling reason to spend time and money for most people.

Some may challenge the idea that games are anything more than a money making business, that all they do is make money and teach how to shoot and act irresponsible. I fundementally disagree, and whilst there are portions of the game development community who care not for there audience, the majority know and enjoy the fact that, first and foremost we are entertainers. I hold little patience for those who see game development purely as software development like any other or its just like writing business software, for me that misses what we actually do, creating worlds that entertain people, letting them experience to places and do things that help even for a short time escape reality.

The tag line of the once great RPG maker Origin was “We create worlds”, which should be the tag line of the entire industry, for it describes what we do fundamentally. Unlike almost all other escape mediums whether it be books, films or tv, games are interactive, for once you direct what happens which ultimately makes the escapism so much more powerful, its not just sitting back and absorbing someone elses heroism or ideas of how things should go.

The logical extension of that therefore is the people who need games to escape the most are those whom real lives are challenging.
For an abused child, the ability to play football on there console with their hero might just be the thing that allows them to survive the horrors around them.
For someone who is house bound due to illness, killing zombies can be the release that stops them going stir crazy, the social contact in an MMO guild might be a needed friendly chat to help cope with illness and pain.
A parent who has spent hours tending to children at their worst, might need a few minutes escape to Peggle to calm down and relax enough to deal with the rest of the day.
Even a well paid middle aged office worker, might need to release the pressure of business in a bad economy, by a few hours late at night shooting in an FPS to stop them going postal for real.

But we have a long way to go, social inclusion is if anything going backwards at the moment. The blogs and experiences of many female gamers attest to huge sexism rampant in many online communities. Most minorities will attest to similar issues, admitting your gay in an online game would almost guarantee abuse. Disabled gamers along with the verbal insults other minorities suffer in the games they can play, find many games simply exclude them completely being unplayable unless you are a picture of health and ‘normal’ function.

Currently the industry ignores it, there is no real business data about how much damage it causes to the bottom line and yet it can take considerable costs to fix so the easy option is to ignore. Having male and female characters (that aren’t wearing metal bikinis) to play, costs art and animation time, extra space on disk/download and even extra writing if done well to at the very least de-genderise the dialog. Ensuring online community uphold the normal social norms and protect people from bullying would be required (in most real communities, shouting “tits or GTFO” wouldn’t be acceptable but its likely the first things most women get if they don’t hide there gender online). Providing proper audio cues for the blind, requires more than just subtitling the movies. Proper controller remapping support and ensuring the game can be tweaked to allow other forms of disabilities to play even more so.

The question the industry should be asking asking is, is it worth it? How many female gamers are there and would be if treated properly, how many disabled gamers are there wanting to buy our products?
From a strict business point of view, it would take economic data that I simply don’t have, though my gut feeling is that it probably would be worth it. However from an entertainment/enjoyment point of view, it easily makes sense, if our prime reason for developing games is to entertain and let people escape, then the more people who can get that via our medium the better.

Ultimate even if its not strictly a win economically in the short term, it may well be in the long term, the more gaming as entertainment becomes inclusive and the norm, the more money will eventually flow into the industry coffers.

The question therefore becomes, how do you achieve the changes needed for inclusion to happen, when the majority of the money men who ultimately decide what can be made, are likely affluent white fit males who care more about the company share holders than the entertainment and escape value of the games they fund and sell?