Frozen - Does Elsa unknowingly thaw ice?
This question(and the entire movie)shows us that Elsa can control Ice and water(up to a point). That being said it would be easier for her to cleanse her clothing slightly in the same way that she was manipulating Ice.
It appears that "Once Upon a Time" is not adding to Canon or canon itself, so instead you will have to use common sense and human behavior. If you wish to call her human, of course.
Is Once Upon a Time adding to Frozen canon?
They wear the same attire every day. Well she just came to a strange place and you have to think about how long she has been there. In the "Frozen" movie she recreated her old dress into a new dress with her power. So maybe she cleanses her dress a lot.
They have magic which takes care of such nitty-gritties. No idea what this means.
They do change clothes but they have multiple copies of the one set of clothes. There you have to admit they do change clothing. If we go into why people wear matching outfits this could get really goofy.
- They like the clothing
- They can't create anything else
They only need to change under-wear. I think this is a valid point when you see that they can indeed(or at least Elsa) can remake their clothing.
I would say it is a mixture of all the answers. Elsa is busy, with ruling and with being dragged out her land. Maybe she never meddles with fashion anyway. So she has not time to get new clothing. Also, why when she can just remake her dress, and has to just change her underwear.
As for Hook I would say that Hook was accounted for in the previous statements saying he had a ship and that he was caught wearing different attire.