Right... Like how Google and Apple and Steam and Microsoft and Playstation compete on transaction fees for their stores?
If the platforms wanted to come after the money, they could. I suspect they're still in the growing phase. But I imagine in the near future, they'll start demanding all ads go through their platforms.
Ignoring the ongoing court cases around that it's very different when you have huge barriers to entry and thus only a few companies especially when they just have to follow the existing norms vs imposing a new norm. Like starting up a video sharing site is hard, but we've seen a number of examples over the past 5 years who have gained traction where we've seen no examples of new successful app stores in that time
If the platforms wanted to come after the money, they could. I suspect they're still in the growing phase. But I imagine in the near future, they'll start demanding all ads go through their platforms.