Why wouldn't you gank bot? Wins all the games.

Because sometimes the enemy bot is at half health, your bot lane has a minion wave pushing on their tower, and they just need that little push to take the point.

Bot is a lane that CAN snowball. If you gank bot, even if "all" you do is push the enemy away so they lose on gold and experience, and it can lead to your bot laner being ahead in gold and even a level, you've done good.

Repeatedly ganking bot also causes morale issues on the enemy team, so long your team doesn't go all "2 bot, gg" the moment you do it.
Repeatedly ganking bot is worth Elo. It's worth a lot of Elo. Do it, it's good.

Also, if you have top, and gank bot, lose top, but then get top, and keep doing it, but you always kill more of them than you lose (cause you retreat responsibly), and always manage to hold 4 points for 10-20 seconds at a time, and 3 points more or less at any given time, you're winning.
Does it matter if it's not the same 3 points non-stop but you keep trading, but are always ahead?

No.

Because ganking bot can get you a point and 4 points is better than 3? It also preemptively counter ganks. For example many people (good players) tend to inmediatly plan an assault bot ff top is of the opponent team (specially if they know they are the kind that like to sit there), so go ganking bot can also help prevent your bot be taken.

My question would be, what's the obsession of people to iddle top allowing the enemy team to do whatever they want in the rest of the map?

You are all bad and you should feel bad >: (

He would just rather be left alone in an eternal mating dance with the other bot laner.

Also, if i manage a chance to play top I usually play assassins, so it's in my job description to gank bot constantly.

It's not that I don't understand that ganks are needed. There have just been so many games I've lost because someone will do it REPEATEDLY without any kind of map awareness. You can see when the opposite team comes out of base. When there are 4 rushing top after a lost teamfight, why put your team at a disadvantage to gank bot when someone is fine down there? It basically translates to: "Oh, we have top, let's lose it for a CHANCE to get their bot". So, I generally disagree. Greed does not win games, considering it's lost me so many.