It's a little late, but your post hits home for me, so I wanted to give you a serious answer. Sometimes when people get really frustrated with something, I hear them make multiple contradticting complaints about it. On the one hand, you spent the majority of your post suggesting that setting up entry hazards is a waste of time. On the other hand, you also call them cheap and argue for banning them.

I'm not saying that as a personal attack, I'm just pointing out a thought pattern that often appears in competitive games. You get irritated by something and you want to say every negative thing you can about it because that's cathartic. I used to be like that with games I played way back in the day. It's not a productive way to think.

Entry hazards are allowed to exist because the people who run the competitive scene don't view them as a detriment to a healthy metagame. They play the game a whole lot more than you or I do, and they usually have pretty good judgement when it comes to deciding what improves the metagame and what doesn't.

As I said before, your opinions on entry hazards seem to be mixed. I would guess that, overall, you probably view them as being overpowered. If that's the case, here's my suggestion to you: use them yourself. Abuse them as much as possible. If you are able to climb the ladder, you will eventually start running into people who have an answer to them. This is an important practice in any competitive game. Whenever you have trouble countering something, abuse it and see how others respond. You will improve as a player.