I had some Airfix WWII sets when I was a kid, and I like to see what other people do with WWII figures and vehicles but I haven't had a desire to collect them myself and I wouldn't want to start now. There just seems to be such a bewildering number of different tanks and guns, how did they ever keep them all supplied? More ships might be a possibility, but not right now.
Ancients for me means Iron age Britain and the Romans; I can see the interest in Ancient Greeks, Homeric Bronze Age and Egypt; I also have some Sumerians (the grand-daddies of all our figures). But there are ancient armies that I have no idea who they are and I'm happy to stay in ignorance.
Fantasy isn't really my thing. LOTR maybe one day, and I do love to see the posts of a guy on Benno's who's doing great conversions for GOT but the other fantasy figures just don't grab me, Well except for the witch riding a broomstick, vampires, grim reapers, skeleton army and Amazons I have, they're just for fun.
Medievel? Agincourt maybe, otherwise no.
For most things it's not a case of lack of interest, just the fact that I don't need extra periods to cover. Even with Napoleonics, just the Hundred Days is more than enough for me to be getting on with.
Even with subjects I don't want to do myself I'm always happy to see them from other folks, and I like all the different painting/modeling styles and skill levels.