There is the aspect that, by wearing a leather or fur coat or whatever, you are normalizing the perception of animals as products to be turned into useful items. That said, I understand people who don't see that as a big enough reason to throw something out and buy a new thing (any production of anything is going to have a negative impact on the world, so using the animal products you have is arguably more vegan than buying vegan products to replace them) but yeah in general this is one of those edge cases where I don't see much urgency in deciding which approach is "correct"

I mean yeah, it's not harming an animal actively, it can be argued that it would be a waste to just discard the item? If someone owns some hand-me-down leather boots that have lasted them a decade the amount of damage they've offset by not buying a dozen pairs of petroleum based boots is worth something.

Does dignity factor in for animals? Would people feel different if the boots were made of dog leather? What if you can't wear petrol based footwear cause you work at the smeltery and normal shoes will combust? What if carnists see your cool skin boots and decide cool skin boots are in this fall and go out and buy them in droves?

I'm starting to get a little silly with it, but I think there are valid questions here.