129
Why aren’t motherboards mostly USB-C by now?
(philip.greenspun.com)
This is a most excellent place for technology news and articles.
You could at the same time ask: "Why are motherboards no longer made for 486DX?". The answer is simple: Time and technology moves on, and USB-A is old.
Take a look at that question again. OP Is asking why USB C isn't standard and you gave an answer as to why it would be standard.