Maybe people hate toxicity and so they choose to leave this game?
That being said, to answer your first comment : there aren't many unique players who have been permanently banned for toxicity.
To get a better idea about what's going on, I recommend having a look at this statistical study made by
@
Lumi
:
A Statistical Analysis of Racism Across 10K+ Replays
Although the title only refers to racism, the analysis considers slurs in general.
I recommend everyone to take a look at it whenever you can.
Here is an extract that should either answer your concerns, or raise new ones, depending on how you currently see the situation.