It's hard to guess the use of a bike from its looks. When mountain bikes first appeared, most of the people who bought them intended to ride them on pavement, and perhaps rarely on trails. Likewise most pickup trucks and SUV's are bought for urban passenger use.
At the time, the perception was that mountain bikes were just more rugged and comfortable to ride. There was a not inconsequential amount of marketing hype about the condition of roads, and the roads in some areas were in fact pretty crappy. Just due to market timing, MTB's were also where most people first experienced indexed shifting, which did improve the ease of riding a bike.
In the case of e-bikes, there's a tendency to get "more bike than you really need" because the marginal cost is acceptable and the motor takes care of the added weight. And from a pragmatic standpoint, the difference may also be mostly aesthetic.
At the time, the perception was that mountain bikes were just more rugged and comfortable to ride. There was a not inconsequential amount of marketing hype about the condition of roads, and the roads in some areas were in fact pretty crappy. Just due to market timing, MTB's were also where most people first experienced indexed shifting, which did improve the ease of riding a bike.
In the case of e-bikes, there's a tendency to get "more bike than you really need" because the marginal cost is acceptable and the motor takes care of the added weight. And from a pragmatic standpoint, the difference may also be mostly aesthetic.