I pick them up sometimes. I have a little stash in a kitchen drawer. Mainly I use them to re-seal bags of freezer food.
I found one on an upstairs window sill yesterday. I suppose a bird was planning to build it into her nest. Incidentally, that implies the birds think it's spring already- as well they might with the mild weather we've been having.
Or perhaps she thought it was a worm.
I picked up a couple just now as I was waving Ailz and Ruth off on their shopping expedition. It's like harvesting blackberries or wildflowers or the pennies people drop at bus stops; I get a lift from it.
I love getting stuff for free.