User blog comment:Woest/Oh flame pants, why art thou so hated?/@comment-25405856-20141010211845

I'm sick of always seeing the flame pants, too. But I was thinking, since she usually requips into them around the end her fights, it's probably because she's out of magic (or at least almost out). Even Erza can run out of power eventually. There are reasons why this doesn't make sense at times, but I think this is at least some explanation of why there's been too much of the armor-not-armor. (She does have Second Origin, which she could use instead sometimes, but that's just Mashima being lazy.)