Do e-bikes generally have regenerative breaking? I assumed that given their weight the amount of energy captured would be very low also bikes have very different braking patterns compared to cars (unless maybe if you're going downhill and don't want to go too fast).
Some electric skateboard do. I think what's stopping many to use it more generally is that you would need to disengage the system if you want to use your bike without the battery.
More complex braking system might introduce a lot of problems to a bike where that should be a simple thing, probably easier to have extra set of hydraulic brakes in case the battery is dead.