Question: how would you do that without rent-extracting middlemen? And even if you are willing to accept a middlemen, why do you think this type of service is not available today? Assume that all the legal barriers for it could be removed - your insurance policy gives you exemption to this and you can have a standard contract defining what would happen in case someone driving your car got involved in an accident, or if you car got stolen by a driver, etc.
If you think that doing that with a car is too complicated, or if you are a cycling advocate: same thing, but for bikes.
Just to make my point explicit: the idea of "trustlessness" is not to get rid of the "trust" in the existing activities that can be handled at the local/"human" scale. The idea is to be able to enable these kind of activities at the higher levels that the institutions (formal or informal) can not cover. If there are things that we can do without a blockchain, great! But think of all the applications that can not be done at all today just because we don't have the tools to enforce the "rules" at a larger scale.
