Yes, and their cut for letting you use the largest storefront out there that THEY BUILT AND GOT THERE, is 30%. If you are earning more money paying that 30% and being on their storefront than you would by rejecting that cut and listing somewhere else, than that is full proof that Steam is earning that cut.

Also, internet explorer came bundled with Windows and THATS why it was deemed a monopoly. You have to specifically choose to download Steam, it gets no starter advantage over the competition.

Steam is the most popular storefront because its the BEST storefront, there is no ulterior motivation putting it at the top, its just that all of its competition barring Itch and GoG are garbage. Steam is still better than the non garbage competition though and why it can get away with its incredibly minor option for built in DRM and its 30% cut. They use their cut to make an amazing storefront, and the developers who choose to pay that cut benefit from the customers that having the worlds best PC marketplace brings.