Earlier quoted context omitted.
Motorcycles are shockingly fuel-inefficient. Some "touring" models get as little as 30 mpg, and few full-size motorcycles get above 60 mpg. While that isn't terrible , it's also not substantially better than a small car, and with much worse cargo capacity and crash survivability.
It's crazy that basically no "fast Velomobile" is in the market. Something shaped like a velomobile (goes 100 km/h downhill by gravity alone), but some what bigger, with a motor and more safety features.
There have been and continue to be efforts to get something like this to market. There are a lot of hurdles.