Because 0.5% of the world population is blind and it costs much more than an extra 0.5% to make a website accessible?
Everytime this question is asked I wonder if people are genuinely not understanding that. It's just not financially worth it.
I'm not defending this position, but it's just glaringly obvious.
Accessibility is about way more than just people who are blind.
(a) accessibility is about all disabilities, not being blind
(b) overall “significant” disability levels are more like 16% [1]
(c) the 16% is at any one time. The chances of us all experiencing disability during our lifespan are much higher
(d) accessibility is a legal requirement for many systems in many regions. Even if you’re not engaging with a region with a legal requirement yet, do you want to have to build from scratch when you do?
[1] https://www.who.int/health-topics/disability