Part of it has to do with what I would call "types". Every era has its favored "types" that define it, and you would find a slew of performers conforming to that type for awhile. Then another "type" would come along to replace it. Hairstyles and clothing suited the "types" at the time, but trying to duplicate that with someone from today looks incongruous.

I can't remember the source, but a casting director was trying to cast for a large Civil War epic or something some years ago, and complained that everyone had abs now, and this was just not historically accurate. It made me laugh at the time.