Not only are repeaters useful and can give you ranges well over 20ks (we can get nearly 300 on our local under ideal conditions) but UHF and AM CB's have more uses than just convoy operations.
Everything has limitations, Sat phones don't always have reception, mobile phones are worse, GPS's can loose signal and lie and UHF's aren't normally used to talk to someone on the other side of the country but they are still an invaluable tool for safety.
We use CB's alot around here to make sure we know where the log trucks are, we aren't in convoy with them or working with them but when your heading up a winding bush road the last thing you want is the suprise of a fully loaded log truck who needs 80% of the road to corner pushing you off the road. It gets even worse when those roads are dirt, one lane wide and 20 ks long, you want the warning so you can pull over safely and let the trucks go. Sat phones and GPS's wont go far to warning you of an approaching truck in situations like that.
Everything has its use and for the cost of a UHF radio (even if it has to be a handheld) anyone traveling further than the city outskirts would be a fool not to have one as a part of their total kit.