More discussion about how both digital and physical accessibility helps everyone:
https://blog.ai-media.tv/blog/why-designing-for-accessibilit...
https://medium.com/@mosaicofminds/the-curb-cut-effect-how-ma...
https://www.npr.org/2015/07/24/423230927/-a-gift-to-the-non-...
This is not necessarily so. I develop mobile apps for a large corp. Our designers are often told by the accessibility team to change their design in ways that make the more accessible, but reduce the usability for normal users. I'm talking about simple controls that most people take for granted, like date/time pickers, carousels etc.
What about your older customers? I have it on good authority old people also enjoy pizza.
And how do you know you're not going to need that accessibility when you least expect it? You don't wake up expecting a retinal detachment or an accident, but sometimes shit happens.
And, though I'm a designer and not a developer, accessibility has had a strong correlation with technical debt. Semantic class names, well structured HTML, not rendering your headline fonts as a bitmap so you can have your on-brand typeface…accessible code tends to go along with resilient code.
Making pages that a program can easily read is pretty fundamental to how everyone uses the web.