Actually, I think that's how a lot of people make their decision. These people decide what OS/ecosystem they like, then whittle down their options from there. But a lot of people probably just walk into the store not knowing what they really want. I'm actually not sure which kind of person is more common.
When Samsung began their marketing campaign, it wasn't directed at you and I. It had very little to do with the Operating System and more to do with cute features the company had added. See 'bump'. The campaign was directed at average users.
It's hard to say who's average, though. At the end of the day, I think it's probably brand name recognition more than anything else which drives purchasing decisions. I'd like to see what the manufacturers know...
Actually, now that I'm thinking about it what I think drove my girlfriend to Android more than anything else is probably how poorly her macbook aged (although with any laptop you can only expect a couple of good years, so she might be being a bit unfair) - especially how awful iTunes is on that thing. Just opening iTunes completely grinds that thing to a halt.
There's really only 2 manufacturers doing gangbusters, Apple and Samsung, everyone knows that. But outside of those two companies the only ones still around are those that licensed OSes, everyone who has tried going it alone is out of business or in the process of going out of business. Do you really dispute this?
BB has a very nice OS, but has done a very poor job of it and spent quite a lot of time backing Adobe's fading tech. There is a lot of room in getting development simpler, but they need to get some more software expertise.
They still have a place if they can start building with a phone at the bottom-end ("free") or low-cost for pay-as-you-go plans. That gets them numbers and then upselling their messaging. Cheap Android lives there (mostly in a poorly implemented non-upgradeable state) and iPhone doesn't.