the cart can be broken and rebuilt repeatedly to create free small containers. While they only hold 4 things, they can be kicked around unlike normal chests (kicked onto a boat, for example...) and they fit in tight spaces around the house.

other than that, in solo play it is too clunky to haul around for my tastes but its not bad inside a large home to store a lot of junk. With the relatively recent update to large chest capacity, I use the cart less for storage too.
The ability to move it around a little inside your base may be useful, eg if you smelt outside but your forge is inside.