[spacerzasp]

>Why would I care about a modular design if I wanted something like this. You aren't going to be a courier one day and then suddenly running Gelato stand the next.

I have a thought like this regarding my compute needs in my house all the time, and then another need pops up, and I'm so glad I can wrangle an existing expensive piece of kit to also cover the new need. Just between the Gelato stand and personal item transport could be one such need

[CelestialMystic]

The need to switch between the examples given is niche (I deliberately chose something I thought was ridiculous to illustrate the point), in a niche market. This is probably why this design didn't last long.

[spacerzasp]

Only because the need to haul anything heavy or large by muscle power is niche. That segment has just been taken by larger combustion or electric engine'd vehicles. Where large loads are commonly hauled with tractors, it's a very common theme to have detachable tools, not tractor per tool.