I think keeping your doors locked is a fundamental aspect to being safe in your car.
BINGO. As a pizza delivery guy in FL back in the early 90s I always locked my doors, and they were not electric. Most guys did not do this so they could run around to the passenger side and get the pies out without using keys to open the door. The prudence of locking them was demonstrated when I was blocked into a spot in a housing project as soon as I pulled in and someone raced up to the passenger door attempting to get in. The MO at the time was to take the driver and car to an ATM and I assume that was what was going on with the accomplice's car blocking me in. Situational Awareness and a locked door gave me the time to retrieve what was needed to drive off the guy at the door who expected an unlocked door. (I kind of stood out in the area and was in and out of there often at night on deliveries so I was an easy mark.)