Now you are really making things up as you go. 20lbs triples the weight of most bikes? That implies most bikes only weigh ~7lbs. You realise that is completely

Now you are really making things up as you go. 20lbs triples the weight of most bikes? That implies most bikes only weigh ~7lbs. You realise that is completely absurd, and would likely be close to a world record holder for lightest production bike? Going faster than other riders is absolutely not the point of pedal assist. Most of them basically can’t thanks to the 20mph cut out. Of course many will find they can sustain a higher average speed below 20, but the point is travelling much the same kinds of speeds with much less effort. Of course rider weight matters. One is rarely hit by a riderless bicycle. Rider weight is especially relevant in your claim that the brakes are worse too - whether the mass is in the rider or the bike frame is going to be largely inconsequential to stopping distances - the brakes still have to stop the combined weight of rider plus bike. Hence relevance of the small additional mass of small motor plus battery being dwarfed by variances in rider weight on normal bikes.