With all due respect, I wouldn't characterize the "bun" as effeminate so much as it looks more on some yogi styles, especially with a beard, and I think some women love that because it doesn't say "9 to 5er". Throw in visible neck/hand tattoos on a dude and younger women (in particular) seem to find it highly attractive (not all, natch).
Looks are just a code to denote your socioeconomic status, your interests, your health, etc., and the code is largely set by the fashion industry. Today's "bun" will be replaced by an updated rat-tail, which will be replaced by clean shaven crew-cuts...etc.