User blog comment:IamJakuhoRaikoben/Chapter 447: Escape Battle, Review./@comment-7418318-20150805221320/@comment-25111584-20150806115541

@Nick: She literally stated that it increases her Magic Power (魔力). Which is why the power of all her Magic is increased. Don't have any idea why you would interpret it as you have. :/ ... Unless you have evidence that the tl is wrong, of course. In which case, could you please provide me with the correct tl? ^^

And it is always better to have more power, regardless of whether she can use it or not. It's known as being prepared. Of course, she can't even face Lamur, but some small task could have arisen.

Comfort? Seriously? That's the last thing on everybody's mind when escaping. Having even a drop more firepower is better than comfort. As long as she is not a hindrance to Erza (please nobody bring up mass), it hardly matters. Obviously Carla's current appearance is for fanservice, but, surprisingly, it actually has an explanation. There are much worse examples of fanservice.

@Bleeds: XD Mashima's real reasons are obvious, but at least he gave us an in-universe explanation.