My guess would be that a cat likes to ensure that everything around him has his own smell on it (in order to mark his territory). Most of your furniture and belongings will have picked up his scent when he rubs himself against it, so he's perfectly happy with that. Then he comes across a bath mat which smells of nothing except rubber (or towelling, or bath salts, or talcum powder, or whatever). That's not going to please him, so he uses the quickest possible method of remedying the problem.
At least your feline friends seem to be choosing relatively inexpensive items to mark their scent on. I once bought a Revox studio quality reel-to-reel tape recorder in a garage sale, which needed a bit of work, for £30 ($45). I had to hunt for a specialist repairer, who took nearly 6 months to source the right parts and bring it back to it's new state. He charged me £100 ($155). So, for £130 ($200) I had a studio quality tape deck which was worth well over £500/$800. The day after I got it back I discovered that it was ruined because it was full of cat pee!
Chris