I feel it's the opposites.
Subspecies are more sensible when you have major generic deviation without enough break from the core species to constitute a new entry.
Like dragonborn who have different colors. Or kobolds who can be winged, draconic, or neither.
I feel the "human with funny hats" happens because TSR, WOTC, and those in their descendants subscribe for low fantasy or at least tameness for PCs. Only the monsters get to be fantastic.
Where are the elves with permanent mirror image glamors?
Where are the dwarves who can turn to stone, metal, gems, and magma and can eat rocks?
Where are the orcs who have primal spirits who can give them increased speed, heighten senses, or claws?
Where are the Lizardfolk who link themselves to crocodiles, chameleons, or dinosaurs to get death spins, invisibility, or thunderous stomps?