If not a panic button as such it is a good idea to have some sort of mechanical control. The computer controls everything in a modern car. It it really goes haywire maybe it won't let you turn it off, shift into neutral. I had to turn off a computer by the power supply switch once, it froze up so bad. The front switch not being mechanical did nothing even after being held for almost a minute.
That being said the brakes are still mechanical and should stop the car. This is a plane but if you can stop an almost million pound plane you can stop a car.