Muscles...
The average porn actor is much more muscular now, even the twinks. Back in the 70's and 80's there were very few muscle hunks in gay porn, and the few there were, all became huge stars. Then AIDs came along and everybody started associating muscle mass with health. But before that you never saw anybody like Dawson, Lucas, or Aiden (from Corbin F.), Johnny Forza, or any of the guys at Gay Hoopla...