My 5 yo cat has always done this and it drives me crackers. I've lost so many chargers to her and obviously it's a fire hazard as well, we can't leave anything switched on. She also chomps on anything plastic - my phone, for instance, and the edge of my laptop. I've taken her to the vets in case she has gum disease or similar - nope.
Anyone else's cat do this? I think she thinks she's a bloody dog!