[randy500]

And to re-iterate, locking the door by the key or the pull rod does 2 things.
1. It locks out the handles from disengaging the latch pawl.
2. A lever also rotates into the latch, effectively double latching the door, its this part that is not worn. You could remove this pawl entirely and the door would lock as it would still lock out handle motion from the inside handle and the outside one.

Some European cars and I think old fords unlock the door when the inside handle is used. these trucks do not because of the design, latch pawl and lock pawl acting on the lock with inside and outside handle disable feature when locked