Glossy photos of girls on bikes!

Or any other naked sportsman photos for that matter?

Maybe its cos men are still the dominant sex after all these years and women are still subjected to sexism, objectification and inequality, even if not as bad as 50 or 100 years ago.

Precisely. Pictures of naked men just aren't quite the same, and don't automatically signify SEX the way pictures of naked women do. The rugby player posters are designed to sell you a product by suggesting that you too might achieve their musculature, whereas... oh, for example, the Lynx adverts have been using scantily clad women for years to imply that by buying this product you too can recruit a harem of pneumatic sex slaves.

Bagsy the top row......
ok 2nd from right. Wouldn't want to be selfish

And this is perhaps an example of the typical behaviour of the 'dominant sex' - to express approval or desire in terms of appropriation and ownership. I came across a rather tedious Facebook group where lots of men had posted pictures of Victoria Pendleton, and almost all of them were captioned "the future Mrs John Smith" (or whatever the poster's name happened to be). It amounts to little more than treating women as trophies, decorations, and status symbols.