I agree that some can. Penny can’t.
She doesn’t like Leonard. She doesn’t like anything about geek culture. She incessantly makes fun of everything about it.
She doesn’t like Star Trek or ComiCon, and none of the other women do either which honestly sucks and is lazy writing, because there are a lot of women out there who do like those things. So the premise of the show implicitly is that “marrying up” for geeky men is finding a hot girl who will tolerate their unhot geeky boy ways.
But she is also not a geek herself in any other way. She is not a scientist, okay.
But Penny is not a geek about anything.

Those girls in high school were drawn to geeky guys because we were closet geeks. We needed those boys to help us let our geek flags fly.
Penny has no geek flag.
Penny is actually just as much of a jerk inside as she appears to be.