I agree except that with my previous bb drive because I could keep adding boost at any speed so I continued to do so, 250 watt motor only but speed when a combination of your self and a low powered assist is fun.
A hub motor (low powered) will only assist to a certain point after that you are on your own, so assuming a passably fit cyclist the hub may only run 50% of the time if that, but with the bb or mid drive you can achieve usefull boost all the time and if you can't resist that boost you use more power but go faster so you may actually use more power.
Now stick a bb 0r mid drive in the trike in my avatar and you will be talking a great jump in effiency due to reduced drag. and you won't see the motor or batteries either.

What we need is cheap safe lithium or firefly batteries now, weight/range is the true sticking point on ebikes I feel, and that weight reduction range increase needs to occur without affecting current price point of an ebike greatly.IMO