Why do we need an all chat?

Dear league community and Riot games, playing League of Legends for more or less five years now the "all chat"-function seems more and more questionable to me. Why do we need an all chat? Why does it have to be possible to communicate with the enemy team? Most of the times the all chat is used to flame enemys or team mates, ask for reports or for trying to tilt the enemy team. Writing things like: "gg wp" can be also writen in the post game chat. And asking for reports is also possible in post game chat. So why do we need a all chat, when most of the people don`t use it properly? Greetings, KissTheDemon (Eu-West)
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