Currently, placing furniture lets you place more items inside them than you can pile on the ground beside them. Last I checked, I could get a LOT more stuff in a huge mound that I could inside a shelf/rack. Additionally, you can have thousands of items in one spot and still find what you are looking for as rapidly as if it was the only thing there.
I was thinking that there should be a modifier for speed picking an item up based on how many items (or types of item perhaps?) are in the same tile (as well as a multiplier for it to be put into storage furniture and vehicle parts) so that if you have a huge mound it takes a while to pull something out.
Additionally, there should be a limit for the maximum volume per item in a storage location, as it is silly that I can fit more 55gal drums in a dresser than I can on empty ground.
The combination of those two should let you have ‘sorted shelving’ that allows very large numbers of small items where you can grab them easily, as well as incentive to not leave huge piles laying around on the ground. You could also have different types of furniture easy to grab things from, such as somewhere meant to hold barrels being slower than a display rack or cupboard.