autonomous droid ships like the SpaceX capsule resupplying the ISS. You just modify the capsule so the hatch is the size of the container(s) inside like a cargo plane. The capsule docks, containers unload, capsule detaches and heads home. Next human ship docks, loads containers, detaches, continues mission.

seems simple enough

Except that seems risky as hell. Much better to have everything aboard ahead of time instead of hoping everything goes right with a en-route logistics chain.

I guess there will be plenty of takers to be the who, but the how is more of the engineering bit. I am guessing if interplanetary travel does become a thing, some kind of open space network will need to be present to facilitate travel.