This is because sofa beds have internal mechanisms and mattresses beneath the seat cushions, which can create a firmer or uneven feel as the cushions and support structures wear down with use. Regular sofas are made solely for sitting and generally maintain their comfort longer, as they are not designed with fold-out frames or mattresses inside. Modern sofa beds have improved in design, but they often still lack the durable seating comfort of a standard sofa over time.
