There are male town NPCs too with eyelashes, like the Angler...
I think it's not actually about whether a character have eyelashes or not, but that female town NPCs have thinner arms and legs and smaller hands.
However this means that most armors and accessories should have female variants too. - most armors actually do has, as far as breastplate is concerned, but accessories are all the same. they would look weird as they are now on a thinner arm or smaller leg,
and it probably would be a lot of work to create female variant of nearly each accessory...