Sneak attack, hello? There are no spells or background abilities that let a non-rogue sneak attack. If a BG thief happens to start a combat round un-hidden, bonus action hide, sneak attack, bonus action hide again. Already hidden? Not in good position? Bonus action dash, sneak attack, bonus action hide. Two bonus actions is huge. If BG thieves lost the ability to pick locks and disarm traps, I'd still make Astarion or Tav a thief.
And if I play a rogue, that is a nice-to-have. But I still won't put up with Astarion for that, other classes have nice stuff too...
