Some chemicals in plastic bags can mimic the smell of pheromones. These pheromones can lead cats to have all kinds of reactions so they can replace their own scent.
Two things are going here: first, plastic has a tendency to hold onto the smell of whatever has been inside it, and second, plastic bags are obviously used to carry things!
There are cases where cats develop a preference for smoother surfaces when it comes time to use the bathroom.
1. Always Start With Medical Issues 2. Remove Access to Plastic Bags 3. Avoid Punishment and Aversions