I dunno. It gets a ton of hype from MCDM, one of the largest sources of fun promotion of RPG things out there besides WotC themselves or GenCon. And there were 23 tickets sold at GenCon. Not tables, tickets, individual seats.
Maybe that has more to do with availability but I'd think a newer generation would embrace PDF and POD more and the original character builder is still out there, no idea if it's still getting maintained but I'd bet it is and works on current hardware/OS.
Well part of the issue is that now its just old and has the inaccessibility of being old.
That and its still a TTRPG. It suffers as much as any other game for the want of a GM to run it, and thats typically the one single biggest barrier to getting people suckered in.