Hi @wp2020
This is actually a good question, if you search around, there are many people bashing MS about this.
As for me, during the years of my IT services, I had also encountered some fair share of issues,
I will focus more on the USB dongles than the bluetooth.
# Dongle Broken - Seems no replacement for that time. Keyboard and Mouse are almost mint condition, user is careless to hit the dongle and it broke.
# Lost Dongle - Also no replacement which I can order and pair to new again.
# * Multiple Microsoft peripherals, e.g. keyboard and mouse, using individual usb, which is using up the usb ports.
IMO this creates alot of E waste and paper weight.
This is one of reason, not brand promoting, I choose logitech products with unifying which have many advantages.
Based on the search, users are also venting their frustration about non user replacement and to be hardcoded and pair at factory
https://answers.microsoft.com/en-us/windows/forum/all/how-to-switch-transceivers-with-a-wireless-comfort/2764518d-b742-4e40-ad7c-e6164ea3c549
https://answers.microsoft.com/en-us/mobiledevices/forum/all/replacement-usb-dongle-for-wireless-desktop/9d888d20-f7be-4da4-a907-bd033cd3547e
https://answers.microsoft.com/en-us/windows/forum/all/i-have-lost-the-usb-receiver-of-my-microsoft-mouse/d6095b6f-b7e8-46ac-ba61-2e413650579e