Page 3 is a different section of the market than "porn". Some may go on to softcore channels and some even into hardcore but for most Page 3 and that type of modelling is a career in itself.
You forgot that some do pose fully nude in the beginning of their career. But once they start to post for those UK men mag they start to think they are better than other models who pose fully nude, and they think are too high class and classy. That why i say UK glam model get ridiculous and ridiculous every year. You can do fully nude and still be called a glam model. Another thing i hate about those UK men mag is they like to lie so damn. Stop telling lies that the model are fully nude in it, because they aren't.