The advantage most other activities have over D&D is that they are much better for networking and showing off known-to-be-valuable prowess.
RPGs are very unlikely to make you any money or increase your status, because you are usually isolating yourself with people you already know, over and over again, and so they have very little visible value outside of themselves.
Other activities, even, now, video games, thanks to online play, are more likely to provide for valuable networking.
RPGs are also much more difficult to pick up for the average person, which vastly limits their appeal over something that basically holds your hand early on, like WoW.
D&D's value isn't understood by most, and only so many people who play it are actually going to USE what they gain from it, and many of the people who could derive value from it probably have way too much of that kind of stimulus as is. It has a fairly limited spectrum, so it's patently difficult to attach any prestige to it.
On the plus side, it's not stigmatized so much anymore that an individual who is otherwise respectable has to hide it.
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Also: If you look at demographic data, you will quickly notice that "normal" is not a compliment.
