There are only a few reasons why a car will be stolen
1.Joy Riding........MK5's can only be driven with keys and most post 2001 cars aswell hence joy ridden cars tend to be old cars
2.Stolen to sell on .....organised crime and involves alot of effort knowledge contacts etc....or steal the keys
3.To perform another task...get away car,ram raid etc......again keys required for a decent car
4.Stolen for parts.......usually involves a tow truck/grabber etc no need for keys etc
So keys are really important to the thief. Keys can be gained with a "friendly" main dealer/ man on the inside
Don't put keys in a key safe as thats where the keys are...quite obvious to a burglar
Keep the keys safe and car is generally safe nowadays.
I have been involved in the investigation of thousands over the last 30 years so happen to know a bit about it