Renault experimented the no-interface approach around 2000 with their car. They had a wireless key that would lock/unlock the key depending how far you were from the car.
Later they added a button to lock/unlock the car because people were not comfortable with the technology:
1. They would get inside their house, drop the key, then get back out to check that the car was locked.
2. You could not just park in front of a shop, because the car could get unlocked while shopping if you got too close. Any activity around the car could end-up in continuous stream of locking/unlocking.
Unfortunately, making sure that nobody can enter your car is one of the primary concern of car user. And if it is not, sooner or later, your car insurance will convince you otherwise.
Later they added a button to lock/unlock the car because people were not comfortable with the technology:
1. They would get inside their house, drop the key, then get back out to check that the car was locked.
2. You could not just park in front of a shop, because the car could get unlocked while shopping if you got too close. Any activity around the car could end-up in continuous stream of locking/unlocking.
Unfortunately, making sure that nobody can enter your car is one of the primary concern of car user. And if it is not, sooner or later, your car insurance will convince you otherwise.