Its a good thing they don't, I just can't imagine you handling mobile broadband, its far too variable.
When I trialed Three 5G as my primary connection for a couple of months, it drove me insane. One day it would be Gigabit, another day it would drop to 400Mbit with three-digit latency and pages failing to load. Its sufficient as a backup and even additional to speed up my Steam downloads, but as a primary connection, no thanks. Not least that the upload can be anything from 2Mbit to 100Mbit and I was recently trying to fix one of my VPS which meant uploading some GBs of data.
This is from a tower that is 82M away from my 5G router.
My FTTP connection is extremely consistent however.