Yeah, HC is an interesting idea. But it’s not the addon, or even the challenge itself that appealed to me, or I think even most people - but rather Classic era being populated again.
I think a lot of people are just really hungry for Classic era in the midst of a Wrath content drought and DF not really living up to many expectations. HC is the only current spark in the Era version of the game, so that’s where people are going.
I presume quite a few current HC players would be just as happy playing Softcore as long as it was as populated with people and communities as HC currently is.