Genjar said:
Same reason why we don't have tags such as undead_humanoid, demon_humanoid, food_humanoid, elemental_humanoid, mineral_humanoid, alien_humanoid, tolkienesque_humanoid, etc.

They're rare, rarely relevant to the site, and (unlike animal_humanoids) most fall under existing species tags such as dryad, alraune, floran, etc.

Having an umbrella tag for a group of tags that are similar doesn't hurt, Genjar. In fact, it helps. People who want to see Florans may notice "Oh hey, Plant humanoids are a tag" and go check that out so they can see the not-quite-Starbound ones.