@JessicaK:
You preempted my posting too.

I especially agree with your last observation about most sex workers having had exceptionally abusive childhoods including spankings. I will lay out how this proves my point.
All spanking is abuse. But let's unpack this.
I have read up on some research on the subject. A disturbing share of parents hit infants. This is abusive and absurd. So is hitting toddlers, which can't possibly work anyway, because toddlers don't understand cause and effect yet. Parents tend to overestimate deliberation and reasoning ability of toddlers. So if a toddler throws a cup of milk on the floor, he or she doesn't do this to annoy his or her parents. The child does not even know about the physics of milk spilling yet. And if it does the same thing again ten minutes later, it is because the kid has already forgotten what happened the last time around.
Nevertheless some 90% of parents spank toddlers and get into the habit of spanking[1]. They stop when the kids fight back physically and verbally and decide that the child is now to old for spankings. The incidence rate declines after age five. Twelve percent of 17-year olds are hit in some way.
Spanking requires some amount of cooperation at later ages and it is a cumbersome, controlled, ritualistic process. That is why abusive husbands don't bother to spank their wives. They just lash out and hit, kick and shove them any which way. So do most abusive parents who beat older kids. This is a likely upbringing of a sex worker.
But for a girl to be spanked until she moves out, you need a rare combination of a girl who does not fight back, call CPS, or just does not bend over plus comparatively "level-headed" parents who don't just resort to easier forms of hitting and who choose to ignore Dr. Spock and changed societal norms about spanking. This is surely incredibly rare. Multiply that with the probability of such a girl choosing to go into porn and you have a virtual impossibility.
[1]
http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=1564&context=lcp