Pierced panels at the ends of seating come from the same tradition as the carved jaali screen, and they solve the same problem in miniature. A long sofa closes off whatever is behind it; cut the ends through and the room continues past the furniture instead of stopping at it. In a drawing room where a corner sofa occupies two walls, that can be the difference between a room that feels furnished and one that feels full.
Structurally it is the more demanding option. A solid arm panel braces the frame; a pierced one has to be engineered so the load runs through the remaining sections of timber, which means the pattern is designed around the structure rather than drawn first and cut afterwards.
Our master Indian artisans lay out the fretwork so the heaviest scrolls fall where the arm meets the seat rail and the finest work sits at the top, where nothing is carried. It looks like a decorative choice and it is actually a structural one - which is generally how good carving works.