Maybe because roadies are more "pure" in their selection. I've been to a lot of shops in my burg and have seen many, many e-MTB's but few e-roads. I built a rigid GT Zaskar that was < 35 pounds with a Bafang BBS02 and small, but adequate battery. The motor and battery probably added about 12 pounds for $700. Perhaps a direction for you. BTW, the motor still lives on a different bike after 10 years. The GT was very "blingy" with a Ritchey full carbon fork, Eriksen Ti seatpost, hand built DT 240 wheels, 11-17-28 cassette cogs and other light bits, but I could have shaved it further.