I like cute chicks just as much as the next guy, but a 25 yr old playing the CHIEF MEDICAL OFFICER for a top secret government project? Puh-leeze.
To the teenage target demographic, a 25-year-old is practically from the Pleistocene Age. ;)
It's TV - young pretty people get all the responsible jobs, while normal lumpy people are villains like your mom and dad.
That said, I never got the Stargate thing, and I'd rather see all of them working on new episodes of Firefly.