It''s not a waste of police time to report a stolen car.
thats exactly why the police exist.
Do you think the police will seriously consider somebody to be a car thief when they are actually named as a driver on the owner's policy and always bring it back to its normal parking space at the end of the day - the same as if a stranger had just taken it off your drive, intending for you never to have it again?
I agree that, normally, it wouldn't overly matter who used which car within a marriage, but that's based on both cars being suitable for standard family car usage. We have a medium hatchback and a mum-bus MPV, so both are practical for most uses; except if somebody is going somewhere where parking is very tight or needs to transport a wardrobe, one of the cars would be more suitable for the particular purpose.
It's very strange - and selfish - to insist on a particular kind of car with very limited practicality, on the basis that it perfectly fits your requirements, but then also keep insisting (without even asking) on using the other car and depriving your spouse of it, because your choice clearly doesn't fit with your requirements.
Most households where they have a sports/show-off/fun car treat it as an additional 'toy' for when circumstances allow them to enjoy it, and also maintain enough ordinary cars to meet their everyday needs. If you as a household need two practical cars (which you clearly do), then you need to get an additional practical car to add to your current one - if you can still afford/justify your budget to keep a third impractical fun car as well, fine; if not, the fun car has to be sold and replaced with the second practical one that you obviously need.