Most sculptures of human form were from Ancient Greek or Roman times through Reniessance and after. It was considered offensive to the model to make his penis large because it was not to be the main focus of the peice, especially if the man was someone important. Also, men had smaller penises back then because they were generally smaller people who did not consume hormone induced foods.

Deepends what sort of art you’ve been looking at!
Do a search for ‘priapus’ to redress the balance::&tbnh=82&tbnw=88&prev=/images%3Fq%3Dwikipedia%2Bpriapus%26start%3D20%26ndsp%3D20%26um%3D1%26hl%3Den%26sa%3DN%26ie%3DUTF-8

It’s small because they were not aroused at the time they were modeling for the sculpture….I think.

The penis is not small it’s just not an erect penis on the statue.

All the sculptors that I’ve heard of were male. Perhaps they were threatened by the model’s manhood and kept it small on purpose. Perhaps the models were heterosexual and therefore not aroused during the posing and therefore small. Perhaps it was really cold when they posed.
What an odd thing to fixate on….