Ethernet
(micro-)SD card
Keyboard
Mouse
Displays
Flashing microcontrollers (technically could be done over BT but it is a pain in the ass)
Gamepad
I've bought dongles/docking stations for all of these devices but it is a huge hassle when traveling, which is a use case a laptop should be able to excel at. Adding just a single USB-A port and HDMI would be a complete gamechanger for me. Apple wouldn't be able to sell as many of their $70 dongles though.
I'm making due with one dongle right now because I have a Thunderbolt adapter and I've daisy chained all my peripherals off of my old Cinema display.
But it's started glitching out with USB devices.
I've found the opposite to be true, with my MX Master 3 using the receiver resulted in some odd "bald spots" on the mat that made no sense, switching to bluetooth fixed it.
Ethernet, 1-2 USB Type A, SD Card, 3.5mm audio, DisplayPort, (while charging too).
As we can see, Apple's 'Pro' products simply do not work me.
That is just what is plugged in to my computer right now, (all USB type A)
How about iPhones, as a great example? :P