Beacause it is broken, most likely.
Because there is a problem with it.
its called the pu$$y
Push all the door locks down manually and then lock the drivers door with your key if it will not stay locked when you push the lock down and shut the door.
a door in your car is not fully shut.
Get a new car you loser.
sounds like a bad door latch mechanism.
If the door is shut then it's probably the switch in that door or wiring to it.
Why do interior lights stay on when engine is shut off on 2001 Lincoln Continental car?
Try spraying latch assembly liberally with WD-40 or similar product and silicone to prevent freezing
to let you know the door is open
Like with Duck tape?This is not illegal unless:You are going to drive the car and this is the only way it is held shut.
to help the door shut more easily