I'm not sure which pressure sensor you mean, like in the brake lever? E-bikes with hydraulic brakes already have sensors for power cutoff (and in this case for brake lights).
Why existing bikes don't use it? Because you need software or a more complicated controller, and the amount of regenerated energy is indeed not that large.
Regen on the front wheel would be most effective - but then you've got two motors or a less-than-ideal front motor that adds unsprung weight and has similar traction issues during acceleration as the front unloads.
It's a shame - I think a lot of people want ebikes to work, but they're not as convenient as a pedal bike (especially not in small apartments) and usually they're too heavy to really use in blended pedaling/e-assist mode.
It seems obviously true to typical racing or distance scenarios. And i notice the wind even at lower speeds on e-bikes in SF.
But between their quad scenario and what I imagine as the urban car replacement scenario it doesn't seem as obvious.
100kg rider at 15 kph = .24W-h kinetic energy. At this speed there is probably roughly 11N of air and rolling resistance, so the steady state power is about 3W-h per km. If you go 1km between stops, or more, the amount you can expect to gain by regeneration is extremely small. It could perhaps extend your range by 5%, generously.
If I'm understanding the math, maybe that scales the regenerative range extension % by your tolerance for pedaling?
If it's w.r.t. effect of low max power on low cumulative generation, I agree it does seem like a little silly to arbitrage your power generation this way. But maybe the tradeoff is worth it in some circumstances in their view?
Or maybe it's just a low cost addition as other commenters say.
Here in Seattle with all the hills it might
I don't see how this would be any different. Or, it's certainly not "moronic"
That combines with the heavy weight of an ebike, another 50lb+ of cargo in the saddlebags, plus my exceptionally fat ass means I burn through a pair of front brake pads about once a month if I'm running errands most days.
So the steepest roads in the world have small sections where the grade exceeds 30%; none maintain it or "average" 30%.
When I'm in my car the dash reads on the hills here between 12° all the way up to 16° on the switchback into the valley. The new market is up a 14° hill.
So closer to ~24% grade average maybe? It's damn steep is the point regardless.