Why guys are obsessed with building muscle?

That's crazy!!! In almost every pic where a guy takes a photo of himself -especially in the rest room- he appears to be muscular... or even if he isn't he pretends to be!!!

Why this sh*ttty craziness with muscle building?

Personaly i'm skinny and proud... and i don't have any desire of adding muscle on my body
Why guys are obsessed with building muscle?
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