I had a similar thought today about e-bikes and other micro vehicles; why do we allow e-bikes to ride on the road, but ban small trucks and tuk-tuks like this one?

https://electrek.co/2021/10/25/i-actually-bought-a-cheap-ele...

Because e-bikes are hard to differentiate from pedal bikes legally and we haven't done it yet, and if you advocated banning bicycles on roads I wouldn't like you very much.

A better comparison, as far as flowing with traffic, is a moped (i.e. Honda Navi, top speed 55mph) rather than a motorcycle (i.e. Suzuki SV650, top speed 130mph).

I had to look it up myself, not being sure, but "the Navi isn’t freeway-legal in many states" [0]

So probably allowing them on city streets but not highways is what I would propose, to answer your question. I don't think banning them altogether is right (for the Kei truck or Navi) since micromobility has all sorts of benefits where it fits.

[0] https://ultimatemotorcycling.com/2022/07/28/2022-honda-navi-...