That kind of "it works better for everyone" stuff is a nice bonus, sure. If you use proper labels for your radio buttons, they get a bigger click target; if you

That kind of "it works better for everyone" stuff is a nice bonus, sure. If you use proper labels for your radio buttons, they get a bigger click target; if you make your app keyboardable, it's better for power users; if you follow WCAG color contrast guidelines, it'll be more readable in any lighting condition; if you write good alt tags, your content will be more searchable; if you use clean semantic markup, it's more maintainable and evolvable over time. But that only goes so far. There's no reason at all to make sure that your accordion widget properly sets its aria-expanded attribute except for people using assistive technology like a screen reader. There's no reason to put role=checkbox on your flashy custom selection widget except for AT users. There's no reason to use aria-describedby to tie an error message to a form field except for AT users. And so on. At the end of the day, for better or worse, it really does come down to caring about all your users.