I haven’t found anything scientific about this, but box springs are wooden slats sideways for even distribution of weight, but wouldn’t the floor be better? Does it damage the bed or affect sleep?
Or are box springs a solution to the manufactured problem of raising beds on bed frames?
Because women will gasp and run if they walk into your room and there is a mattress in the floor.
You need to ventilate under a mattress, at least in a climate/room that is not dry.
In Japan people sleep on cotton mats on the floor, but they move the mat in the morning to get it out of the way and to air it.
There is also a comfort consideration with having high beds that are easy to get out of, especially in our sedentary western lifestyle where most people are quite stiff.
They’re about having a comfortable entry level rather than having to stoop down; they’re about having additional shock absorption to reduce wear and tear on mattress; they’re about airflow through mattress for comfort when sleeping, keeping it from smelling/letting sweat dry more quickly, letting dust settle through
People generate a surprising amount of moisture in bed. If the bottom of the mattress is on an impermeable surface like the floor then the moisture will build up there and cause mildew on the mattress. You need ventilation under a bed.