I love Battle Maps. If I were to hazard a guess, the maps most "in demand" are decent battle maps. When I want a map _fast_ , it's not a big regional map. Oh, I've got nothing but massive respect for the cartographers here who make them. But if I want a big regional map, it's likely specific to my campaign. (Yes, I admit it -- RPGs are the main reason I'm into maps at all). So I'm more likely to try my hand at making it myself.
But battle maps! I might need one of those fast, if the PCs decide to wander off the beaten track. So the more of them I have, the more likely I can throw a battle together with visuals, instead of hand-wavy "yes, he's within range.."