Why don't fitness models flex biceps

I love the pictures of like ordinary girls flexing biceps.  I think its hot. But i also want to see the professional fitness models flex.  They do all these sexy poses but many of them NEVER flex their arms. 

WHY ??????

I think its viewed as not so feminine ... i guess ...?

if they want to keep a "glam" image, they don't flex. figure, bikini and fitness contests don't have flexing either. but paysites have lots of fitness models flexing, so it varies from model to model.

In the US (dunno about Canada) there is no flexing in fitness competitions, in Europe, they DO flex... maybe US competitors kinda got 'used to it'

There's also a little stigma about showing female muscle here in the US, even yet... ya don't see many FBB's in magazines anymore, either...