The hair has lanolin in it and that's what makes the pins slip into the material easily. I always do this with my needle when I am quilting and it gets sluggish.
I use my pins even when they are not their best. I have a container that I use these pins in and when I need to block something I have crocheted and starched, I use these to pin them to the large piece of cardboard I keep just for that. When they get too bad I put them into a pill bottle.