Why ban for 14 days when you can just permanently chat restrict? Riot just ban me from chatting. Really.
Because its not Riots job to prevent your toxic behaviour.
You got chat restricted, which is a warning that you have to change your ways. You chose to ignore those initial warnings, so now you are suspended, and make no mistake: This 14day suspension is your final warning, the next stop is the permaban.
In short, Riot is not obligated to shield others from your bad behavior...you are obligated to exhibit acceptable behaviour in the first place.
If you can't do that, there is no reason to let you play the game.