When I bought the 2016 Toyota Tacoma, apparently it was a very big deal that the tailgate now locked to prevent these thefts.
I've never had a reason to remove it on the F-250 (which I sold this week, so I can't test it now), but on two previous F-150s and a Jeep Comanche, they were really quick and easy to remove.
Still don't see where the market is, unless it's a self-perpetuating market of people who had theirs stolen looking for a deal on a replacement.