Balance is just as important in a single player game as it is in a multiplayer game. If balance is broken in a single player game and its far too easy then there is no challenge which svcks a lot of gameplay value out of it.
A question for you. Could you happily sink 50 hours into a character with tgm enabled from start to finish without getting bored?
I'ma fan of the game so, yes I could play it from start to finish.
It's not like I start out incredibly powerful, I have to work my way up.
As for balance, let's not even discuss it.
The game is unbalanced to begin with.
How about a Death Claw surviving a blast from a Fat Man with almost no health lost?
Plasma Rifles doing almost nothing to some characters?
People enjoy the ride of getting stronger and building their skills.