Basically, if your statement is true and its a generalization but there is an explanation, Glamour modelling for so long was THE thing in the UK. Firstly hardcore porn was banned in the UK for a long time, we also had Page 3 Girls. In the 60s,70s and 80s and for some of the 90s these girls were superstars. Some of them made three times what other models earned. Magazine modelling also earned the models more money than porn could.
From my chats over the years with American website owners and models, Glamour was never a big thing is the US. The money was in porn.
However the UK has some excellent porn actresses , evidenced by the fact that a lot of them are ranked very high on Brazzers' network by their subscribers.