Why is muting normalized?

Hi everyone, I am still new to the community, been playing since October or November last year so my opinions may be from ignorance. My question is why is muting normalized and advised? when I started playing ranked and asked for tips people said "mute all" I didn't listen to this cause I am rarely bothered by flaming and honestly I suck(I am still new) so most of the times the flaming is justified.

I just don't understand why a game this complicated that relies on strategies and teamwork people would normalize muting, even muting ping, doesn't that affect the team? how will you know when your team is trying to do something? I mean this is a multiple player game you have to interact with other players and your actions do impact them.

I just don't get it.