Originally Posted by
NotABadger
I suspect because then Marvel wouldn't have had the big crossover event they wanted!
But really, much as it pains me to say it since she's probably my favourite character, Rachel just isn't that popular, certainly not at Magneto's level. She's not going to be the one to win a big crossover for the good guys, regardless of how powerful she is.
If we leave Marvel wanting to make money from Fatal Attractions aside, then in universe I don't see Magneto vs Phoenix going Magneto's way.