The problem is that any Ubuntu phone that is released will likely be just as locked down and filled with bloatware as everything else with Verizon.
If Canonical were smart, they should also work with handset manufacturers on a clean version of their software without all the crap - the Nexus phone approach. When given the option, most people opt for the crap-free phone. I have a feeling that if Canonical does not push this option it could really tarnish their name - like how Microsoft is always associated with viruses and malware.
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.
"open/flexible" is a double-edged sword.
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.