Leather Wheeled Backpack Why Does My Cat Love To Lick Leather?

Why does my cat love to lick leather? - leather wheeled backpack

I had a backpack with wheels, the leather straps on the back. One of my cats lick the skin for several minutes at a time. My other cat totally ignores. I read on a website it is a symptom of internal parasites, but the two cats have recently been wormed. In addition, the other cat does not.

Can someone tell me why my cat does this and is it dangerous? There should be no chemicals in the skin, which, as I suspect are toxic. But my cat has been done for several months, it would likely be toxic to the health problems are now.