So, I agree in part.. But there is another side to this.
Quick question: The need to earn 100$ before they pay out, is that per month, or just as soon as your "balance" with them reaches 100$? Ie, if you made 50$/month in sub fees, would they pay you after two months?
Now, just paying everyone, from one sub on up would be expensive, extremely so. I certainly dont know how their contract with whoever handles the payment transfer stuff and all that jazz works, but its going to cost *something* for those transfers. It may be a bundled deal, or a per-transfer, or based on the total amount of money transferred over a specific amount of time, etc, but I can understand why they would require you to reach a certain number before transferring your funds. Thousands of transfers a month potentially of nothing more than a dollar or two would be cost prohibitive in the extreme.
Next, the rights they have to control your likeness and everything.. well, thats a pretty sticky issue. My GF is a photographer and there is a whole universe to this sort of thing.. But at the same time, and I dont mean this to sound like a douche, Im just playing a little devils advocate.. so, at the same time, you are using a service they have created - a free service. Tens of thousands of lines of code, christ only knows the amount of data transfer, insurance, employees, servers, techs, marketing.. Twitch is an enormous machine that you can use, free of charge, to benefit yourself in any number of ways and its completely free. Them requiring you to hold content (I dont imagine its something they often enforce, but assuming it is..) isnt a terrible price to pay for the benefits the service offers. You dont have to agree with their contract and your free to use another service, create your own, or simply forgo streaming.
My personal thoughts on the affiliate program are not positive in the least. I just listed what I did above to play a little devils advocate, as I stated. I personally believe the affiliate program is there to actively discourage donations - because Twitch doesn't get a piece of those. Since you can support your favorite streamers via a Sub button in some cases, the affiliate program gets more buttons out there without the effort of vetting the streams, so when people want to support a non-full sponsored streamer they enjoy, they're just as likely (or more so) to click the button rather than go through a donation procedure. In all honesty, it almost surprises me that Twitch doesn't have a donation framework in place to try and get pieces of that pie as well. I understand the handful of reasons they dont, just saying.