Tangent, but what's the rationale for car doors requiring slams? They are the only door I know, at least in common, daily life contexts, that require slamming them with the force of Thor to properly close them.
However there are minivans with electronically operated sliding doors, which either power the latch allowing you to gently close the door, or (going further) powering the entire closing operation at a button push. I surmise the reason we see it moreso on minivans is because 1) it is particularly difficult to work up enough energy to properly latch a sliding door, due to losses from the 90-degree change in direction at the end, and 2) violently slamming the sliding doors on a minivan is very dangerous to children's fingers.
I'm not sure how much money I'd pay for it, but it's a nice feature.
There is also a third, dumber reason, at least for cargo van slide-doors. The surface area of sliding doors are large. When the door takes that 90 degree turn and moves very fast towards the vehicle, it is pushing a lot of air into the vehicle. The air in the vehicle has nowhere to go, so it acts as an air-spring, slowing down the door. To properly latch the door, you have to really slam it hard. If the windows are down or an other door is open, the sliding doors latches very easily. I thought I was going crazy when my door was closing easily ... sometimes. Some cargo vans even have vents that allow air to escape, but people tend to cover them because they don't know what it's for. But electric sliding doors also solve this problem, by moving slowly and letting the air escape.
TLDR: if you car door doesn't close, open the window :)
Often, the door just isn't aligned correctly. Either it's sagged on it's hinges over time, or the latch itself needs a minor alignment/adjustment (Note that even on a lot of new cars, this still helps a lot! Not all manufacturing is perfect). Other times the rubbers can be hard and perished and it doesn't allow the mechanism to engage properly.
I've always found it amazing how much less slamming the doors needed when a window was left wide open and the air inside the car could escape freely.
On one of the cars it wasnt enabled from factory, but I asked the dealership and they enabled it at no cost.
A car door is like a bedroom door in the same way a MacBook is like a Cray supercomputer. A door is a door and a computer is a computer, but there is significant variance within that category.