The recent Dragon Boat holiday here in China afforded me and my family the time to travel to South Korea. Although Korea is a very developed country bicycles are still very much in use as cargo carriers. In fact about 90% of the bicycles we saw in Seoul were used for this purpose. Which is to say that very few people are riding bikes just for fun.
The layout of these bikes was quite different from cargo bikes here in China. The frames are typically welded, not lugged, with fatter tubing. This modern construction means that no double (or triple or quadruple) bar reinforced frame is needed.
Instead the forks and the rear of the bike are usually heavily reinforced. The forks often carry up to as many as TEN fork trusses, attached to both the stem and the handlebar.
The bike geometry also tended to tend to be long and low. The stretched and reinforced rear end often having an extra set of bracing between the seat stay and the chainstays.
Cargo is carried on a truly massive rack on the back. The racks look more like a hand truck welded to the back of the bike with large pipe extensions up and backward in an "L" formation to which cargo can be secured. My thought is that this was originally a backpack type frame which was adopted for bikes. In some of the shopping areas we saw similar racks with shoulder straps so that goods could be carried up stairs. These same type of racks are also seen on motorcycles.
Have a look the picture below and you can get an idea of how massive the carrying capacity of these bikes can be. The package rack...and the cargo... is actually much larger than the bike. And this one is only partly loaded!!! The forward tilt of the rack helps keep the bike from flipping over backwards.