Perhaps where you are at. I worked at a small community college until a couple of years ago and still take classes there in the evening. I also work at several elementary schools, two charter schools, two home school/school hybrids (edit: I forgot about one). At the college, in one semester, I found about two dozen kids in three departments (multimedia, culinary and computer science) that played D&D, Warhammer, Dark Heresy, and Vampire. There was little overlap between individuals and groups. They were playing with friends from work or whom attended other schools. None of them learned from parents.
At one of the hybrid home school/elementary school (I forget the term they use), there is a weekly game club where they play D&D one afternoon and another rpg another day. Several of the elementary students with whom I work with at regular schools also play. At some of the schools, the afterschool D&D club is run by one of the competitors for the company with whom I contract.
I also know of schools on the east coast that also have gaming clubs at elementary schools and junior high schools (those are run by some game designers and others working in the gaming industry often at their children's schools).
Here in Australia when I posted for players for 3rd Edition games I'd get flooded with responses. Now? Maybe one response every 3 months.
But that's all anecdotal besides the point. I find it a great stretch of the imagination to think that TTRPG's are growing at the same rate as MMOs/CRPGs.
If D&D is growing at lets say n YoY, and the RPG industry as a whole is growing at n YoY, the total percentage of RPG customers playing D&D is shrinking, because it's a much smaller number to start with. If you're looking at preventing your business from becoming more and more niche, you're going to want to tap into that larger market.
D&D is not competing just in the TTRPG market, it's competing in the entire RPG market, because its players require time to play it. Time they could spend playing other RPG products.
Before Everquest there was Baldurs Gate and such (and going back further, games like Might and Magic), but those games didn't compete for time with D&D, they complimented it. Now, D&D needs to actually compete for time with these MMO's and other CRPGs which spew out DLCs to keep player engagement.
There are much more young kids playing MMOs than there are playing D&D, and if WoTC doesn't focus their efforts in that market, they don't have much of a hope really in the future. Sure, the percentage of D&D players will slowly grow (until perhaps we all start to die out), but so will the overall population, and it'll end up more niche than it is today.