The mechanical “handbrake” is designed to work without being tied to electricity, which means that when the battery is dead in the car, you can easily remove it from the handbrake, say, in order to push it. With an electronic analogue, such a thing “will not work.”
And the “handbrake” is easy to fix in a certain position, which will be extremely useful during the buildup of the car when slipping in snow or mud. The push-button parking brake is far from always ready to block the pads in the desired position.
With the “handbrake” it is easy to dose braking, as well as give the car the opportunity to slide in a turn. True, we still do not recommend repeating a similar procedure on public roads, and even without certain skills. Such pirouettes are only possible for experienced pilots, who often use this technique when maneuvering during sports competitions. But the electronic parking brake and the like are not able to create.
Finally, repairing or adjusting an electronically controlled brake will be much more expensive than in the case of the classic version of the “handbrake”.