Well, if the armor is insulated, then it should (in theory) protect against lightning, force or no force. But I haven't seen any insulated armor in star wars. It is easy to overlook the fact that while star wars revolves around force users, their number on a galactic scale is actually very small, and if you consider how few of them actually can produce lightning bolts, it's even less relevant to have insulated armor (armor, not workman's coveralls). You bring up a good point, there does seem to be some kind of double standard as to what counts as force energy (lightning, drain, grip) and not force energy (blasters, telekinetically pushed objects, etc.), but since star wars is basically medieval fantasy in space, it kinda makes sense - a magic energy shield can protect against spells, but not against arrows. But come to think of it, it does indeed not transition well into the space age (I.e. energy weapons). And you know, when in doubt, blame it on magic (and midichlorians).