No key and lock combination is truly secure and in this respect they can only ever be considered a deterrent. Someone can either duplicate the key or create something that can serve as one. Failing that, they can simply force the lock mechanism. If you don't believe this then this is one good example video that proves this point.
The usefulness of a lock is also largely dependent on the structural integrity of the door to which it is fitted and the door frame around that. There is no point in having a very secure door lock, if the door can be kicked in in a few seconds. Modern external doors have internal strengthening and multi-point locking. They also come with a solida frame that is rigidly fixed into the wall.
The same could be said of keyless and electronic locks but, at least they can provide flexibility and notifications and logging of when doors are locked and unlocked. They can also be configured to capture images and video on use.