It does not make it consumer choice friendly.
No, but that is not illegal. In the end, consumers need to decide what they want and the type of ecosystem that meets those wants.
Yes, let’s not bother fixing a broken system, let’s just make everyone change professions.
Developers chose what OS they will focus on knowing the ground rules; and those who develop for iOS likely saw that iOS is a profitable OS and that made it attractive. No one forced them into that choice.
Is this something you apply to every mono- / duopoly or just the ones you identify with? What do you like most about duopolies?
Perhaps because, while 2 OS's are dominant, there are plenty of manufacturers of phones for the consumer to chose, it isn't a duopoly. Even the top 2 vendors have less than a 50% market share. There are phones all at various price points and feature levels, giving the consumer plenty of choices as what to buy. They can even chose a phone that uses a different OS, if they chose, and still interact with the 2 major OS's.
All this whining about choice comes down to how to divide the profits, not to help the consumer with lower prices. Look at what happened when Apple lowered their cut to 15% for small developers - how many of them said "Hey, Apple just reduced our costs so we'll pass on the savings to help out the consumer?" versus simply taking the windfall profit?