Bascially, because almost all fanboys of old Fallouts don't participate in any Fallout wiki and so on?
And only thanks to them, to that big (old) Fallout fan group that trademark was so valuable... what lead in effect to creating "great" Fallout 3 by Beth...
Look for example at Arcanum, great game, even in some ways better than old Fallouts but hey, it never had big amount of fans so no one bought rights for it...
Also, look at age. Most Fo3 fans shouldnt even play this game, looking at criteria. It shows how it attract teenagers, who played games like Cod etc. and Fallout gave them not only fps exprience, but some wasteland and some crpg (in their recognition) fun..., which wasn't know for them. And almost every first game for specific genre is for specific person the best one, at least, for some time.

And yeah, I know now, that someone can write "I played Fallout 2 and Fo3 and liked it too." I know... but it's a few from a millions.

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