We already make car wiring insulation out of soya-based plastic, which is highly biodegradable and palatable to micro- and macro-organisms of all sorts.
Which is why so many modern cars have weird electrical faults and fires.
Which is why so many modern cars have weird electrical faults and fires.
It seems like they could incorporate capsaicin and other deterrents into the polymers, but that probably isn't pleasant for individuals involved in the production process.
Not sure what the point of your question is, though.
Meanwhile with the exception of wires in high-temperature areas, PVC just doesn't do that.
Aside from that ... this is not an anecdote vs anecdote debate, these wires have been around for decades and this exact question has been studied scientifically. The degradation rate and wire-chewing prevalence are comparable with PVC.