This pretty much goes along with that reddit question I saw that essentially asked, why does riot prioritize verbal issues (racism, toxicity etc) over other forms of negative behavior and so on. Basically if it isn't there for their little chat filter bot to see then Riot can just play out of sight out of mind.
Basically Riot doesn't care about anything but verbal toxicity by non-popular streamers. It took XWX trying to sell his Riot given pro account before Riot finally did something about his very obvious boosting.
I hate to bring up that guy (who I won't name) that got banned recently, but he had 5 (I've heard 7 but I only know of 5) accounts permanently banned and still Riot was letting this guy make more, as he streamed daily. We have multiple cases of pro players trolling and being VERY toxic even in chat on stream, popular...erm...heavy chested streamers (I don't know a better way to describe them without leaving out their name) who were well known for intentionally feeding and trolling that were never banned.
Riot can tow the PR line all they want, and give us those all popular "stats", but it is fairly obvious that if they can't record it in a word document (ie chat logs) then they take it less seriously. Why do you think we will never have voice chat? They have no way to police it (and have said as much).