Police need stricter criteria before they can legally search a vehicle for a couple reasons. The first is that many citizens don't understand their rights and grant permission to search, not realizing that if they don't grant permission, in many cases their vehicle can't be searched. Also, a vehicle is moving property of the owner, and just as a home can't be searched without a warrant, a car should not be able to be searched based on probable cause. Police can claim too many things as probable cause too easily.
We definitely should have stricter rules to warrant a vehicle search. Searching a vehicle without the proper authority is an invasion of privacy. There should be very strict rules to search someone's personal property. The government already invades our private lives too much. They need better reason to invade our lives further.
Law enforcement officers are using the vehicle search clauses to easily invade people's privacies on the road, to harass drivers they know or make their life hard. It would be beneficial that stricter rules could be put in place to limit the abuse of these searches and stop at the same time, a criminal part of law enforcement.
There shouldn't be stricter rules to warrant a vehicle search, because the law enforcement already needs reasonable, articulated suspicion in order to search a vehicle. Unless a vehicle is impounded or the officer thinks that evidence might be destroyed by a time delay, they also usually need to wait for a warrant. Courts provide enough oversight of the reasonableness of searches that we don't need to make changes to this procedure.