If you're lucky enough to be gaming in perfect health, with perfect vision, perfect hearing and perfect teeth - though those probably aren't too important for most games - it's easy to forget that not everyone is. The more thoughtful developers put in additional help tools, like optional subtitles for sound effects as well as dialogue, or simply avoid the common blunders like using red and green indicators. Far too many however simply don't, either thinking it too expensive, or just forgetting to put aside the time.
AbleGamers has put together a special, free, booklet to cover what disabled gamers need - and just as importantly, why they're important. Download a copy here especially if you work in games.
Key areas covered include the obvious colour-blindness issues, along with motion related issues (such as the distance on the screen that a cursor has to travel), hearing, the need for difficulties to take into account potential physical limitations in addition to raw skill, and cognitive issues like having to juggle multiple actions and inputs simultaneously to accomplish relatively simple tasks.
The book doesn't say that games shouldn't have challenge or anything close to it - the organisation previously gave the original Dragon Age its "AbleGamers Accessible Mainstream Game of the Year" award and that game was a complex beast for a mainstream title. It simply wants developers to think about the audience a little more broadly, and take the time to do small things like adding a symbol to a health bar to show your character is poisoned instead of simply turning it green. If letting more people play isn't a good enough reason to put in the effort, hopefully selling more games will be.
Let's all agree to never, ever use the word 'Includification' again though, okay?