Doesn't seem odd for Asia to me. I think throughout much of the ancient world penis and vagina totems of a sort were very common at shrines and temples and the like. Still very common sight in Asia especially in more rural areas.

I think it was largely the spread of Christianity and Islam that considered such practices to be a form of heathen idolatry that ended the practice in Europe and the Americas. Though you still saw some echoes of it in European Renaissance art where the copied the Greco Roman styles including the penis or mammaries. Like in Michelangelo's David as a prime example.

I think the US side took a far stronger "iconoclast" approach towards depictions of sex likely due to the influence of the various religious separatist groups that settled there. One thing that has always baffled me is the supposed controversy over nursing in public. Which is something I've never considered to be any more offensive than eating in public. Which is to say there's a time and a place but it's hardly scandalous.