The current implementation, which is more or less just “Each citizen becomes a humanoid vacuum cleaner”, shortcuts many things that I think are pretty nice in the “normal” way of moving things.
There’s the whole visual aspect: You can see your hearthlings move stuff, which adds to the cute factor. Most prominent example would be building: Imagine how dull and weird it would look if they just went to a stockpile, loaded up a bunch of wood and stone, then just casually walked without resources to the construction site and started building a cathedral, while you can’t see anything more than a hammer sometimes.
Then there’s the gameplay aspect: They can only move one resource at a time, which simplifies a lot of things. Because of the iconic system, where all entities are supposed to be stocked at a size at most 1x1x1 blocks, carrying a bed or carrying a log has the same dimension. It wouldn’t make a lot of sense to be able to carry more of these things, it wouldn’t make sense to allow, say, carrying 10 logs or one bed (i.e. different “carrying stack sizes”).
Of course, usability is part of it, too. You can see what they are carrying at every time, you see how the resources “flow” around (because they are carried around). If workers can carry multiple items, which can hardly be represented visually, you would have to click through some GUI or HUD to see what items those are. You couldn’t interact with those items either easily, because they, well, aren’t there. It also raises the question of how item removal works: What if the worker dies? Are the items just splattered on the ground? Are they lost?
I think the current system works fine, not to mention that point-to-point actions are much easier to do than solving the travelling salesman problem… for multiple salesmen.