Well the iPhone didn't come to Verizon for years because Apple would not let Verizon put its bloatware on the phone. Verizon only caved because Apple sales were so strong. iPhone only comes with Apple software, you have to manually download any Verizon apps.
My parents both got Androids recently, and while you can "hide" the pre-installed bloatware you still can't delete it. It took me about 30 minutes to clean the phones of all the widgets and crapware.
As the newcomer, a Ubuntu phone really wouldn't have any bargaining power and would be as bad or worse than Android.
Part of the problem of an "open" system is that the very flexibility/openness means your position is weak - there's very little you "can't" do.
Especially if you do it for one carrier - you can't easily say no to the next one.
Whereas with Apple, the carrier has no idea if the product is capable of their needs, and besides with the Apple brand it will sell millions regardless.
My parents both got Androids recently, and while you can "hide" the pre-installed bloatware you still can't delete it. It took me about 30 minutes to clean the phones of all the widgets and crapware.
As the newcomer, a Ubuntu phone really wouldn't have any bargaining power and would be as bad or worse than Android.