I worry about the safety of 20-30MPH and trying to stay with car traffic. e-bikes make more sense to me as an assist for riding at normal bike-like speeds than as a way to ride at moped speeds.
I should clarify that on the bike path, I generally do stay in the 15-20 MPH range, as there are many pedestrians traveling at low speed. On the road however, staying at typical bike like speed actually feel more dangerous to me. It kind of feels like driving on the highway at 45MPH when everyone is going 75MPH and a bit nerve wracking.