Yeah see - why not just say chargen ends and the game starts when you fail a survival roll, rather than have some powergamer try for his munchkin 15+ times until he gets it?
What you're basically saying is to use the Optional Survival Rule. The reason you don't want to do that is that it takes the fear of going another term out of the game.
There's no risk. There's nothing to lose going another term. If you fail survival, you'll just start the game.
And, all the PCs start to look like 30-34 year olds.
Your powergamer probably wouldn't go 15+ times because he'll get some damn good stats eventually--and he won't want to give up that character because he's so good.
"OK...you've killed three other characters in character generation. But, this one has incredible stats--not a single one below a 7. You've gone a term...do you want to risk another term? Or, are you happy with the three skills you got during your first term?"
What I used to do is pre-select where character homeworlds. I'd roll up a nifty, high-tech world, with lots of opportunity for a new character. Then, I'd rule, if you died during chargen, your character would be from a second planet I had prepared--not so high tech and not so much opportunity.
It was a little encouragement, without house ruling chargen, for the players to go with their first character. It worked quite well, actually.
There are other things GMs can do, without a big, sloppin' house rule, to encourage players to not automatically join the Scouts if they don't like their character's stats.
And...what if they don't get in?
That's what the draft is for.
I played once with a powergamer new to Traveller who rolled up a character he thought wasn't so great (I thought he was fine). He missed enlistment into the Scouts, then I made him roll the draft. He got into the Army, made every Survival Roll, and went to max terms--where he was discharged.
And, this old and creaky character is the one he was given to play. He tried to "game" the system and ended up with a character he really didn't want--and could have taken his original rolls and turned them into something he would have liked playing.