Well they tolerate it because there is no other choice. You can't say f** all the apple users.
Would you have the same argument if Windows took a 30% cut of all transactions that happened on "their platform" ?
Would you have the same argument if Windows took a 30% cut of all transactions that happened on "their platform" ?
Then there are the network effects. Many apps have a social component, and if your app isn't on iPhone you'll only get the customers who both use Android and who never want to collaborate with iPhone-owning friends/family/coworkers.
This is of course true for iPhone-only apps, too, which is why folks argue Apple and Google are a duopoly: it's infeasible to succeed in the mobile market without bending to the gatekeepers, and they don't give anyone the market power to force them to change.
And yes, if Windows wanted to charge 30% then go for it. It is their platform.