I don't think "most" mice and keyboards are USB-A: bluetooth peripherals eclipsed wired peripherals ages ago.
Yes, most of the decent new ones charge via USB-C.
Yes, most of the decent new ones charge via USB-C.
Before I stopped counting, I found 8 wireless keyboards using bluetooth, 9 wireless keyboards using a USB-A receiver, and 10 wired keyboards using a USB-A cable. It seems like USB-A is still alive and well in the peripheral ecosystem.
Here's a link to the search results page I used: https://www.komplett.no/category/10264/datautstyr/pc-tilbeho...
It's a website which is commonly used by gamers, so wired keyboards may be over-represented compared to the general population. But it clearly shows that actually, USB-A is still really commonly used in new peripherals sold today.
I think Apple (correctly) determined that these folks will tolerate whatever they put out, buy adapters to use their beloved special keyboard, etc. And for the ones who won't tolerate it: they're probably not buying Apple hardware anyway.
EDIT: Just to respond to the "gamers and people who code are in a different class" thing: I went to a different store which is more general, went through the most sold keyboards, and skipped all "gaming" keyboards (so everything from Razer, everything branded Logitech G, everything with RGB), and counted to 14 bluetooth keyboards and 19 keyboards which require USB-A (7 wired, 12 with the USB receiver dongle). People just use USB-A peripherals a whole lot. (Store URL: https://www.elkjop.no/INTERSHOP/web/WFS/store-elkjop-Site/no...)
I am surprised that most peripherals do still use USB-A to charge, and my argument did change to reflect that new information.
The only keyboards I counted as requiring USB-A are ones which are wired with a USB-A cable, and ones which are wireless but only have the ability to use an RF receiver dongle such as the logitech unifying receiver. Your mouse would be counted in the "Bluetooth" category.