I prefer to look at making things accessible in two more positive ways:
1. It's a challenge; any designer can slap together a slick looking website. It takes thought and creativity (and research) to make an interface that is inherently flexible and usable by just about anyone.
2. Sure, you might scoff at the market possibilities today (seven percent? who cares!). But as life expectancy goes up, so do the numbers with disability, and the longer someone is alive, the more money they are likely to have. Reap those baby boomers! (cynical, yes; but this is business after all).