The reason why little Pieck always showed up with messily tied hair is since she doesn't have a mother, her father did it for her all the time. She knew it's messy, but she still loved and kept it because her father tried his best to do it.
Funny thing is dudebros are saying Mikasa looks like "mankasa" now that she literally has MORE REALISTIC body design than ever. Just say you never seen a woman's body in real life and go.
Can't blame them, though. Why would women want to get close enough to be seen with losers.