If you can turn it off by design, then I really can't see anyone being able to prosecute you for not having it on or refusing to pay out on a claim through the insurance. If having it on is optional (i.e. you can switch it off by using a switch) then you have the option to switch it off. If it was mandatory to leave it on in the UK then VW would design it so that it could not be switched off (except by VCDS hack).
What's next? having a parking scrape and the insurance refusing to pay out because you chose to ignore your parking sensors because you normally deem them to be overly sensitive?
There is no current law that obliges you to keep it switched on at all times, and if it is non-operational in 3 years time, you would currently not fail your MOT for it not being operational (imagine that test- "we're going to drive your car behind our van, both vehicles will be doing 40mph. The van will then abruptly brake and if your car doesn't plough into the back of it then you've passed"