The only way to get off a level 2 or level 3 dive is if the laner and jungler have really good synergy, basically meaning one has strong burst and the other has some form of hard CC and on top of this, if the laner doesn't just run backwards (what you're rarely supposed to be doing) and hits back at the one taking turret agro, then unless the one diving flashes away, then he'll die as well. Not to mention the fact that YOU should have flash as well, unless of course you had to flash away from your opponent or else you'd die, which means getting dove is how you get punished for sitting in lane after that fact. Also, you need to be a good early game jungler to pull these off, which you should be considering and in the case of getting pushed backwards, warding the bush behind your turret. If you really don't want to take risk, you simply back, but this could risk putting you behind if the enemy has waveclear.
If we buff turrets to the point in which dives simply become impossible, then this game will make losing lane or just outright losing the game much less effective, dragging games out for way too long. It pretty much makes snowballing near impossible and the only way to repeatedly dive your laner by yourself requires you to be at least 2 kills (or just an abnormally dramatic CS lead, which should only happen in cases of counters and deaths, or else you're just missing last hits) ahead or a champ that's really good at diving (fizz).
Though to be honest, once you get into the late game, the tankiest of champions really don't give a shit about your turret (I'm talking things like maokai here). The thing is though, usually the one tanking has to sit back, or risk getting bursted down and losing the teamfight, which usually means it's pretty much a 4 v 5, which if you're losing that, probably means you're so behind you DESERVE to lose. Especially if it's the late game and you're getting pushed back; usually means you messed up somewhere, and should lose.
TD;DR Dives only happen so early if the jungler and laner have really good synergy, the ganker is really good early, and most of the time results in a flash from either the jungler or top laner (depending on who tanks). Also, you have to put yourself in the situation through poor play, meaning you deserve to get punished. Plus you need to be around half health, if not drastically lower.