Why do people always instantly counterswap?

Like, it's so lame. Every time I queue for comp, if I get a single kill in the first teamfight, especially if it's on a hero genji counters (zen for example), that person will almost always try to hard counter me.

Like, do these people even enjoy the game? How do you enjoy letting the enemy dictate what hero you play? I don't get it.

Honestly it only really bothers me when they pick either sym, or zarya. OR when 3 of them do it at the same time. Yesterday I got a 3k and the enemy switched to zarya, mei, sym, moira. Like... why not just try to use actual skill?

Maybe its just because I'm plat 1, I heard that's where the most counterswaps happen.