Alien sculpts aren't for everyone. It's something I've noticed in wargaming that "human" models tend to sell better.
Sure there are some exceptions like the Tyranids, but overall when I see alien races being created they are almost all "humanoid" in shape. The variations tend to be left to either an "animal-like" head and "digitigrade legs".
I'm trying to create something more alien-looking that isn't like other alien models I've seen so far.
I suspect that a lot of it comes down to people buying things for familiar environments - 40k (or not-40k), Infinity, Near-Future, Starship-Troopers type marines vs something, Star Wars, etc. There are people who want weird, alien, entirely new things, but they're fewer in number. On top of that, of those who do want such things, many want a complete line or at least a couple packs, with soldiers, command, support, maybe civilians, and so forth, because they want groups large enough for army-sized games or large skirmish.
I think this may change a bit as smaller and mid-size skirmish becomes more popular and the number of games grows so large that there's a bit more splintering in the game scene. If I were doing a sci-fi project (tentative plans to do this once I've done a lot more pulp stuff, but that's a long ways off) I'd certainly be interested in all sorts of weird and unique things. Humans are plentifully available and perhaps a bit boring in excess.