I think this is a major part of why nothing happens. Every time Phil's an asshole, I'm betting there are dozens of reports sent with poor spelling, poor grammar, and a bunch of references that anyone who's not "in" on DSP would not understand.
If, instead, people wrote measured reports without hysteria-driven ranting, and provided actual evidence (see, for instance, the whole "fundraiser" thing), that might result in something different.
But given that people try to @ Twitch and TwitchSupport on Twitter all the time, I doubt that's going to ever happen.
Piggybacking off of this, but there are also a lot of "boy who cried wolf" style reports with Phil. After the initial fundraiser temporary ban, anytime DSP mentioned anything relating to money was met with talks of reporting him. I think people are even more likely to make reports in the moment if they're watching the stream/restream/whatever. Obviously nobody but a Twitch employee can confirm this, but I'm guessing they look at a few of the reports, then end up ignoring the rest.
Part of it is the smaller the channel, the more chances they give. A large part of that has to do with optics. Ban enough small time streamers, whether or not they did something worthy of a ban, you risk one of them spinning the story and gaining traction about Twitch censoring up and coming streamers or punish them for not making money. It's the same reason Twitch is harsher on the larger channels, because those channels breaking the rules is all but guaranteed to get negative press attention, so Twitch needs to distance themselves as soon as possible.
DSP is too much of a nobody to go viral these days. It'd take something big, like him jerking off on camera or breaking a rule that could potentially put Twitch in legal trouble to make them care. Phil being whiny and toxic in his tiny bubble doesn't put Twitch at risk. Using YouTube as an example, there's tons of channels doing way worse shit than PewDiePie paying someone to hold up a sign saying kill all jews, but PewDiePie gets crucified for it because of how many viewers he has and how famous he is. It was bound to start shit, so YouTube had to jump in and do something, otherwise they'd be spun as the company that supported antisemitism.
All that being said, I think like most things in DSP's life, he's his own worse enemy and he will eventually do something that puts him on the radar and earns him a ban. There have been a few close calls before with Phil shitting on other streamers and companies. I think this is eventually going to do him in. Someone as big as Ninja isn't going to care about Phil enough to report him. For Ninja, it wouldn't be worth the time or risk of drama to get into it with Phil. Ninja is also probably internet savvy enough to at least know some of Phil's reputation, which makes him even more of a "who cares." It'll probably be someone smaller and less experienced who goes through the process of reporting Phil. I'm guessing this is why the one time he did get in trouble for insulting someone, it was some rando that even inside the goutsphere most people couldn't tell you his name.
Anyway, usual disclaimer that this is just an explanation of Twitch's view, not trying to white knight them, they're still massive hypocrits for not enforcing their rules equally (if at all) etc.