Lawrence Alma-Tadema wasn't the only Victorian-era painter to use ancient backdrops for his paintings as a cover for nudity. In France, William-Adolphe Bouguereau didn't even bother with classical settings.
I think painting or drawing the human body - especially nude, and especially certain aspects - has always been challenging. It’s something an artist would enjoy working at for many reasons. (Even the human hand has seemed especially difficult to master.)