To put into perspective, when Epic only takes 15%. They themselves admitted that is not a sustainable thing. EGS is constantly losing money. So now I invite everyone to gauge just how "big" the EGS is. How many "features" they offer etc. This platform in so much smaller than Steam and even they state that a 15% cut is not sustainable to keep the light on.
Judging just how big the Steam platform is, do people honestly think Valve could be forced into reducing their cut to this proposed 15%? When this little hobbyshop that is EGS cannot make it work. Why would it work for a much much larger and therefore more expensive platform?
I am furthermore given to understand when you distribute on Steam you are free to run your own store front. You are free to create your own Steam keys for your games and sell them in your shop which is supposedly have a 0% cut for Valve. Of course then you would have to run your own store with all the effort and cost that go along with it. Or you simply put it on Steam. A storefront visited by millions of paying customers. Which handles everything. From purchase/refund/CDN for Downloading and updating the game binaries/communityhub to directly engage with the customers if you wish
In the end, the only way they are forced to use steam is because that is where the customers are. and since there are alternatives around, these customers could very well shop some place else. but they dont. they shop where they get the best experience. and if that is on steam, thats where they go.
If "developers" were really honest they would all disclose just how much they sold on Steam vs any other digital store front in case they distribute their offerings to any store that will let them. Just because you get 4 sales on Epic vs 4 million sales on Steam does mean Steam is a monopoly. It just means Epic is a steaming pile and given the chance the customer goes to the better option.