Does Supergirl really need to be buffed up if she gets her powers from the Sun? Same with Superman. Their strength doesn't have anything to do with the size of their muscles.
This is true, but then you see things like this:



And of course you have the men:


I understand when you say that muscle size isn't necessary. And technically that is true. The girls don't need to be full on body builders. That would be over doing it. But I would at least like them to try and give them at least an athletic appearance. Last I saw Gal Gadot still has the whole fashion model thing going, certainly not what one expects from a super heroine, especially when one of her powers is strength. I think Caity Lotz is probably a good example.

Some nice musculature and definition, but not a potential eyesore like Ms Olympia so it won't detract from the sex appeal they are obviously shooting for when leaving the bikini models in there.
Look at Henry Cavil up there. The same principle could apply to him. He could be as defintionless as I am and the super powers could easily explain his abilities. Apparently someone felt it necessary to bulk him up a bit and I'm glad they did. It just looks like a better fit.
Edit: Formatting.