I will disagree, you can see the entitlement of users that demand the game,movie or payment system must be exactly his preferred one. Though for Valve you can compete with them (but people hate it but I think they don't hate the actual competition but the shitty implementation of the stores and the fact this game launcher most of the time must be run in background ) BUT with Apple you can't compete, they have up to 50% market share in some countries and if you are a business half of your existing customers(that you earned fairly and were not gifted by Apple to you) will ask for an iOS app and now you either give a bad experience to your customer or you pay the tax.
About the argument that Apple,Valve gives you access to many users, sure that should be price correctly, developers could pay for getting promoted on the first page of the store, but Apple,Google should not get a cut for promoting my app if the user installed it starting from my own website.
About the argument that Apple,Valve gives you access to many users, sure that should be price correctly, developers could pay for getting promoted on the first page of the store, but Apple,Google should not get a cut for promoting my app if the user installed it starting from my own website.