If government regulations are going to insist I have to put that investment in day 1, I'll just take up badminton or something.
It's not that hard, and if every developer spent an afternoon looking into things, they'd realize how easy it is to get it right if the team is aware of it.
I'd not mind if like developers need to go through security and privacy training, they'd also go through accessibility training. A little investment would go really far.
They all handle accessibility well, you just need to remember adding labels to your icon buttons, and you are good to go. If you don't reinvent the wheel thinking your buttons are soooo different that it needs to be rewritten from scratch, things just work.
For example, the ADA doesn't require employers to accommodate disability needs until a business has 15 employees.
Of course, culture is a huge factor. The US wasn't built on "regulation, or else", it was built on "if you can, do". This makes business boom, but makes other concerns, like welfare, an afterthought. And it's up to debate which system is better to exist in. People dislike the rules, until it ends up benefiting them.