What's really on the edge is your attitude towards users with disabilities. Your users with disabilities. You know, your customers!?
Every time you dismiss accessibility as "just an edge case," you're basically saying that one in five people don't matter. That's not an edge case any more. That's a massive chunk of potential customers you're telling to sod off.
These aren't hypothetical users we're talking about either. They're real people trying to pay their bills online, book holidays, order groceries, apply for jobs. And every time your website fails them, they remember. They tell their family. They tell their friends. They shout about it online. And they take their money elsewhere.
Your "edge case" is someone's mum who can't see your tiny grey text. It's someone's brother who can't use a mouse. It's someone's daughter who needs captions to understand your promotional videos.
Accessibility isn't some nice-to-have feature for imaginary people. They exist, they have money and right now they think your product is shit.