This isn't keeping ad-tech in check. Twitch itself is an advertisement business. They continuously have increased the amount of ads they run. (for people who don't know what this is about, twitch has introduced rules that keep banners on streams to 3% of the screen size and banned 'burned-in', that is independent ads run by creators)

The entire point of this is the same as Reddit's, to take away direct revenue agreements between creators and third parties, so they can take a cut on every transaction made. How can anyone on earth hope that internet monopolists ban independent revenue channels for content creators? Google is also an advertisement business. They will never ban sponsorships, they will just force everyone to use their APIs.

There is no need for anyone to moderate this for the very simple reason that you, as the watcher, can simply turn the stream off if you don't like what the streamer shows you.