I think a lot of you are right about a lot of points.
I'm sure it is "just a job" to many commercial models. And equally sure that some find it interesting as well, or grow to find it interesting. In all the DL relationships I know, one partner tried DL play because the other suggested it, and then liked it. Seems like it could happen "on the job" as well.
I personally am only interested in amateurs, because the whole fake aspect of the commercial models pretending to be into DL play just turns me off, totally. I've seen a few gorgeous girls in nappies re-posted form pay sites, but still, it is just a fake. I want real! (And I prefer real women to starved-thin 20 year olds.)
And I especially agree that the improperly taped diapers are the giveaway. Anyone who likes this game quickly learns how to tape on a nappy!