There is a market for them, so manufacturers make them. Basic utilitarian transport.
It's the really bodgy conversions that fascinate me. They've got that African vibe of "we'll do whatever it takes to get it working, as long as we don't have to buy new parts".
Sometimes extending to the carrier bags waterproofing the battery in the frame triangle! But again, it's good when viewed from a utilitarian non-ICE transport pov: have bike, start rooing, discover it's hard work, add motor...