Why must pace always be fast moving?

It would appear that currently there's no longer any room for the less than fast paced novel. Every top ten book list seems to be filled exclusively with fast paced titles, usually thrillers. So where does that leave reflective writing with its slower pace and greater emphasis on the inner lives of characters rather than on action per se? And what does it say about today's readers who seem to have an insatiable appetite for breathless plots that twist and turn at breakneck speed?