We need to know the measurements of our rooms because when we build it if it were for real life we would need exact measurements for everything or it would fall apart. Also the measurements are used to make sure they are up to state standards. A designer would need the measurements to know how big you can have a chandler, if it needs stairs, and if you’re selling it how much it would go up for if in perfect condition. With area you can decide how much paint, wall paper, and flooring you need to furnish a room and if you want a indoor pool you need to know the biggest it can be without disrupting standards.