As a computer idiot, why can't current systems have what old computers, games, phones, etc used to have which is a little red 'return to factory settings' button on the bottom?
It's technically possible but to do it you'd need to tie that button into firmware so that when pressed it loads up a ROM copy of whatever settings are changeable then writes those settings to the HDD.
But to ensure that it actually worked properly, it would have to remove any and all updates as well as other data which may interfere.
So it may actually need to wipe your entire HDD and reinstall the OS. But doing so requires a sizable amount of storage space. Plus it makes it so easy to essentially erase everything that little brothers would do it just for fun. And since the console isn't designed to be bricked so easily (old games required you to put in IRQ settings and the like) then said button is essentially worthless.
It's far easier to simply have the technicians have a way to boot from a USB drive into the console and reinstall the OS. Not only do they make money on repairs, but they also ensure that your data isn't wiped without your consent.