Power steering is another matter entirely. I know you probably meant to say power brakes- but a similar situation exists for electronic, drive-by-wire steering. I believe a few manufacturers have attempted dbw steering, but abandoned it due to safety concerns. Here again the aircraft industry has taken the lead. Just a matter of time before this tech makes it way into autos.
Good catch, you're right about the Power Brakes. Sorry 'bout that.
Regarding aircraft and electrical braking: The difference between airplanes using brakes and cars using brakes has, in my opinion, a major difference: Congestion.
If an airplane lands with busted electric brakes where the default option is Max Braking, the worst that's likely going to happen is a bunch of shredded tires, not loss of the airplane and passengers.
If a car blows a fuse when surrounded by other cars at speed, max braking
might not end up with wrecks rear, left, and center, but I wouldn't care to lay bets. With the current failure modes on hydraulic brakes, the default option is
no braking, with effort required, one way or another, to slow down - but under the driver's control.
It's a chicken-and-egg problem: Electric brakes work fine, so long as BRAKE!!! is the default with no power. Which works fine for airplanes, but not cars in traffic. Asking for user control of electric brakes when.. well.. there's no electricity, then that's a problem.
That's why I mentioned cable braking, something that that ancient VW I mentioned happened to have. The idea is to have a completely independent stopping system, powered by human muscle and nothing else. In that VW's case, hauling on the emergency brake pulled a double ended cable laid in a pair of tubes along the length of the car; the cables ended up on one shoe each on each rear wheel. I'm suspect the German engineers who designed the VW bug were just looking for a cheap way to implement a parking brake.. but, geez, one could lose
all the hydraulic brakes and that blame cable system would work anyway.
So, I have zero idea what an electric disk brake looks like. If, instead of having hydraulic pistons, electric brakes had a rod going to a lever to actuate the disk brake on one side and an actuator on the other, maybe attaching a cable in parallel with the actuator might do something positive. But that means Interesting Mechanical Engineering. Might still be cheaper.
As I said: I'm not adverse to the idea of electric brakes. It's the work-in-case-of-failure cases that give me the willies.