Furniture sold in a box for the buyer to assemble has moved from a budget novelty to the default across much of the market. The advantage is logistical before it is anything else.
Assembled furniture ships mostly empty space
A finished wardrobe or table is largely air, and a lorry or container filled with them carries very little material for the volume it moves.
Freight is priced by space as much as by weight, so shipping assembled goods means paying repeatedly to transport nothing.
Flat packing raises the amount of product per container several times over, and that saving repeats at every stage from factory to warehouse to shop.
Warehousing and retail space follow the same logic
Storage costs scale with volume, and a warehouse holding flat cartons holds far more stock in the same footprint than one holding assembled pieces.
Shops can display one built example and hold the sellable stock as boxes, which turns a showroom into a catalogue rather than a stockroom.
Self-service collection removes delivery from many transactions entirely, shifting the final and most expensive leg of the journey to the customer.
Damage rates fall when nothing is assembled
Assembled furniture arrives with joints under stress, corners exposed and finishes vulnerable to knocks in transit.
Flat components stack, brace one another and can be protected cheaply with card and film, so fewer items are written off before reaching a customer.
Damaged flat-pack items also fail as a single replaceable part rather than as a whole product, which makes remedy far cheaper.
The design changed to suit the box
Engineered boards cut cleanly, hold fittings predictably and behave consistently, which suits machine drilling to tight tolerances at high volume.
Cam locks and dowels replaced joinery that required skill, and the whole vocabulary of construction was rebuilt around what an untrained person can do with one tool.
Rectilinear shapes dominate because they pack efficiently, which is why the aesthetic of the category converged as much as the engineering did.
The costs sit with durability and disposal
Fittings that are assembled and disassembled repeatedly loosen, and engineered board tolerates moisture and repeated screwing far less well than solid timber.
That shortens the life of a piece and makes moving house a decision point, since many items do not survive being taken apart twice.
Disposal is also harder, because bonded composite board is difficult to recycle and second-hand demand for it is weak, so the saving at purchase reappears at the end.