Yeah, I think it's a combination of things, the "sales" part surely has been considered, the construction (although you can look at phones like the LGV20 that did a pretty good job with a removable battery), and I think the "battery quality" plays a lot into things too, it's completely un-controlled.
Look back, you can find where iPhones had some overheating issues (I don't recall which version, in the 2's or 3's I think), which were mostly tracked back to bad replacement batteries. Various laptops have had the same issue, and fewer and fewer laptops have replaceable batteries now too, hmm...
I think *most* people want to change phones every couple of years, or thereabouts, so I tend to discount the number that are "accelerated" by the battery dying, but that's IMO, nothing statistical that I know of.
Edit: I should mention, that I had to go some pretty serious lengths to find a secondary battery for last WinPhone, my 950XL, it was quite the research project to find an actual OEM/non-knock-off battery (there were tons of the latter available).