> How has allowing competing browser engines on Android helped the web ecosystem?
By allowing people to install Firefox. Would you rather that Android be Chrome-only? Neither, I suspect, would Mozilla. The same applies to iOS, with its backwards browser holding back the web. Your argument would justify Microsoft making IE 6 the only allowed browser on Windows. Do you really not see how ridiculous that is?
I think you'll find the answer is "no." Not allowing competing browsers does not help the web ecosystem or the users. It helps only Apple.