I honestly don't get that complaint and it crops up every time there's a relaunch. Two books. Six books. Twenty books. We are never obligated to buy...
The X-Men basically have too many characters to get all the important ones in a book at the same time. Even with 6 team books, and removing everyone...
'Why?' Just to see the disappointment on your corn-fed, gee-whiz face, Superman. And because a great dark voice on the edge of nothing spoke to me and said you all had to die. There is no 'Why?'