Because Twitch has already been struggling to pull in advertisers for years and is retroactively changing how ads function on the website in the near future. Even subscribing to a channel might not matter anymore.
Not to divert too far from the original topics intent, Twitch's ad-rate percentage is so pathetically small for larger streamers when compared to FaceBook gaming or even YouTube. It's why most actively refuse to run them and opt for overlay sponsorships and paid-for playthroughs instead. This upset the higher ups and most channels have been forced to either run ads at set intervals or the channel will auto-run ads at randomised points. Sometimes lasting more than 2 minutes for a 15 minute block of viewing. That's 2 minutes lost of your own content and potential new viewership. In turn, Amazon has invested heavily into finding ways to FORCE users to experience ads. Even if you use specialised ad-blocks as a plugin, Twitch finds a means to overpower the code within 6 months. You know, instead of fixing important things site wide...
Plus any sort of "outrage" isn't needed when they are still suffering the reputation as a cam site by the general population. Legit trying to get Hasan banned wouldn't harm him with his current reputation. He'll just hop onto YouTube or FaceBook and be given all the high end perks as he's got a devoted following much like timthetatman, Dr. Lupo, Disgusted Toast, Ludwig and other recent absentees.