I commission art, which is expensive, time-consuming, and depends on artist availability - pretty much everything I've ever made from the game has gone right back into art/music commissions haha.
There are a few other characters that don't have art as well (Olivia in Ashley's badon scene, the Knight-commander, etc), everyone having art is pretty recent. For most of the game, it was just text boxes or a mix of text boxes and art.
Male Sam was an experiment that didn't go nearly as well as hoped, while making it much harder to update female Sam, so unfortunately he is getting removed in 0.22. There will be other bros in the future (no NTR).