How is it possible that there are so many trolls out there?

I'm not a high elo player, i'm only half gold. However, to get there, you have to tryhard a little bit and win a fair amount of ranked games.

How is it possible that i had 3 trolls in my teams today. (in 3 different games).

The last one confessed that he was using another person's account. But come on, 3 different people (or 2) who make it to half/low gold just to troll?

and that was only today...