I think it is because X-men TAS (1990's) was released on the era where the fans of the comic from when it was released were still alive or still had interest with X-men.
Evolution was good but it was released a decade after, and then there's Wolverine and the X-men released 8 or less years after evolution. With the number of cartoon shows on the rise in this century, it is hard to keep the fans interested especially if not a lot buys or knows the comic too well like in the 90's. Noting too that X-men was originally released in the 70's that's 40 years after (counting 2010).
What worries me is that the number of fans seem(I may be wrong) to be depleting decade by decade, but still x-men is the best thing there is out there! I've only been a fan since 1996 sadly. And it sucks that there are funding issues, cant they realise X-men is a symbol of generations and generations of undying legacy! For something to last this long means that it deserves credit. If naruto can survive, why can't a comic thats been alive way before our parents even married. Gladly, there are movies (which hopefully hollywood wont butcher) coming.