Don't actually use a mobile phone except for emergencies so in car glove box switched off most of the time. Costs me around £5 per year on payasyougo. It's a common assumption that everyone has one and people are confused if you can't provide a mobile number.
Yes that is true, I do remember 2 situations pre-mobile phones that I came across which would have been helped so maybe I should carry it around a bit more. Still don't have to switch it on unless needed.