Cars have safety interlocks. Just not the one you described, which wouldn't make sense anyway. Only being able to start when in park is a pretty common and sensible one.
And ebikes already have safety interlocks too. One is too high a throttle voltage when it's turned on keeping the controller from activating.
Also, a car has pretty robust protection these days, crumple zones and airbags etc, so high survivability even in a big crash. And a blender might take some fingers off, but nobody is usually putting their face right in it in a way that will kill them. And I'm pretty sure the death rate for leaving the air conditioner on with a door open is pretty low too, depending on your dad when you were a kid lol.
But ebikes are fast enough, heavy enough, have low rider protection, heavy injury penalty in a crash, and often of such shoddy construction that it suddenly kicking to full power isn't far fetched, and often operated by less bike savvy older people that have bad reflexes and damage easily. So it seems like an interlock or two isn't the worst idea in the world.
Or maybe getting squeezed between that bus and the curb as it was turning where suddenly giving up braking and sprinting out of the turn at top speed was the only way out, then looking for an escape route while I tried to slow it down again made me see it as a good idea. It sure didn't seem to take any of my autonomy for making my own decisions away after putting one on
P.S. Tiger, I think he just meant why interlocks on one and not the other, not bike quality of life vs cars.
Chalo and I don't always agree, but he's a pretty good bike loving car hater too lol.