It was a Jim Lee/Rob Liefeld thing, apparently. Pretty much all of the first-wave Image artists were superstars at Marvel for a few years, where they created what we now know as the nineties aesthetic: pouches, big future guns, etc.
This era of X-Men, and of Marvel in general, is when Bob Harras was content to let the artists do the plotting and asked his writers to simply script for them, which is part of what led to Claremont quitting in 1991.