I always have, to me it's just that integral politeness. I appreciate when people take the time to tell me thanks so I try to do the same. It just feels to me like you're not even noticed if people don't even take the time to say thanks.
Same with people who don't respond to comments. Why should I bother if you're not going to acknowledge me?
Lol yeah, I've been noticing that more and more... People are getting really weird about what they accept as polite and rude. It's... idk. I don't if their page says don't, but I do if there's nothing. Same with faves. Unless you're faving tutorials or references. I don't really thank for those.