You are REALLY pissed off about this - its hard to have a real discussion when all you do is QQ.
The truth is, it is NOT beneficial to under tower. Like it or not, that is a fact. If you have trouble every time an opponent goes under tower, perhaps you are just bad at sieging? I don't know, you seem reluctant to give details on what the hell you are talking about.
The game is a STRATEGY game. Its about SKILL and DECISION MAKING.
So, since you neglect to give an example, I will create a theoretical one.
You are fighting me. I am mundo, you are Trynd. (I don't know, you just act like a trynd/yi player) - you just beat the crap out of me and killed me, so I tele back to keep you off my turret.
Now I have some options (some DECISIONS you might say) -
A) Walk out and fight out again, despite being no better equipped to do so
B) Try to use the minions as a cover and CS to the best of my ability, pushing away from my tower so you can then fight and kill me again
C) Play safe, and try to stall and get help from jungler.
A SKILLED player, would pick C as the most advantageous choice in a bad situation.
Now YOU have a choice:
A) Push like an newb, and fight me anyway, cause lol is now street fighter the 3d map expansion.
B) Ignore me, cause if you dont hit me, you dont damage me, so no turret aggro - but that means tons of free damage while you cs/hit my turret under my tower
C) Freeze the lane via good last hitting and assist your team in some way while I try to farm with out leaving hte safety of my tower (and if I do, you come fight and kill me again)
Seeing as we are even having this discussion, I'm gonna guess you picked A, though maybe I underestimate you, and you chose B instead.