I love the sidecar action in your country. They're not nearly as common here, and I rarely see sidecars for transporting humans. Usually a motorbike and sidecar rig here would be transporting pigs or selling grilled eggs. I don't know why but the traditional Cambodian way is a heavy trailer behind the bike that can sit up to 4 people or more. These small bikes work really hard to move that much weight and passengers, so steep hills are not possible.
I love the moto choices in your country too, seems a lot more bikes are off-road friendly there.
I guess, it's easier to use sidecars compared to having a trailer behind the bike. I case of pedicab going uphill, some drivers would get off the bike and start pushing the bike together with the sidecar.
I think most of them are off-road friendly indeed. I guess it's because most of them are also used in the countryside. :)