Routing the mechanical linkage to a place in the door that would make sense for a door handle to be is the difficult and expensive part.
Bowden cables are dirt cheap.
The cables are cheap, designing a door latch system to be easy to install/cheap to manufacture is not. Why do you think all parking brakes on all ICE vehicles have turned electric now?
Probably because forgetting to pull the handbrake is a very common cause of accidents?