Why the whole bed
Most beds are assembled by accident. A sheet set from one place, a duvet cover from another two years later, a throw that was on sale. Nothing is wrong with any single piece and the bed still looks like three decisions. We sell the four layers as one edit, in cloths and colors you choose a layer at a time, so the accident cannot happen.
What we sell and what we do not
We sell the cover, not the insert. We sell the protector, not the mattress. Those are the two pieces people replace least often and ship worst, and leaving them out keeps the price of everything else honest.
The cloth
Washed cotton for people who want the bed plain. Sateen and satin for people who want it smooth. Bamboo and lyocell for people who sleep hot. Flannel and fleece for four months of the year, cotton muslin for the two in between. Every cloth is chosen on its own merits.