Accessibility typically doesn't cost much. With many modern OS UI frameworks, you get it for free as long as you don't go out of your way to customize shit that you probably shouldn't be customizing in the first place. If you stick to standard controls and not try to use crazy ways to override user preferences, your application should be accessible to things like screen readers mostly out of the box.
As with most things, this is an issue of education and awareness. It's not that most developers intentionally break accessibility, but rather that a very large number of developers simply don't even know it's an issue, let alone something that they should keep in mind.
"customizing shit that you probably shouldn't be customizing" is kind of a standard in video games.
Video games are not meant do be productive, they are meant to be fun, and standardization is boring. It means that they can't completely rely on OS frameworks to make an appealing game, it means that accessibility needs first hand consideration.