I can imagine it now, Jungler gets mad at me for something, mutes my pings. Now 3 of the enemy are running down my lane taking my turrets after a succesful gank. I'm pinging to alert my jungler but he has me muted. Team gets first tower and half a second. Rest of the game they apply heavy pressure to the one lane while split pushing another ALL because the Jungler decided he rather not listen to pings.
It already happens without the mute, muted pings will only be much worse.
ANOTHER SCENARIO
Top lane mutes my pings, Mid takes me down and wonders up to top lane, Im pinging MIA but he cant see it or hear it. He gets the kill and now the top laner is mad at the mid laner telling the mid laner to go this and that when really he should be mad at himself. All the while because top couldnt see pings the mid laner has to deal with a fed mid lane enemy. This all could have been avoided without muted pings.