I think the latter is the real explanation. We(geeks) in general tend to be loyal to our shows. If we take to an actor or two we then follow them around to other shows even if its not sci-fi(eg Boston Legal-Shat, CASTLE-Fillon, BONES-Boreanaz).
When it comes to some peoples vote for GBOW they go with a high vote for Firefly,ST or nuBSG(especially tourney time) over others.
I didn't watch Eastwick
and am frankly so-so on Eureka
but she is gorgeous, imo, so I went thumbs up even though she wasn't ST