Acting Career: Age-span of NPC on Set

All NPC on set are "Adult". I play 200 sims (active & passive), but none of them is adult. Since it seems to be a requirement for NPC at the studio, new adult NPC are created for these roles. 

I would really like to have family & friends as makeup artists or co-stars. So why doesn't the game pick jobless sims from young adult to elder?