Pocket springs are a premium feature primarily used in the seating and sleeping surfaces of high-quality furniture:

• Sofas, Couches, and Sectionals: This is their most common application in living room furniture. They are used in the seat cushions and sometimes in the back cushions to provide superior comfort and support.
• Armchairs and Recliners: High-end chairs use pocket spring systems for lasting comfort and proper spinal support.
• Beds and Mattresses: While this is a sofa-focused question, it's worth noting that pocket springs are the gold standard for mattresses, for the same reasons they are great for sofas.
• Ottomans and Benches: Some well-padded ottomans with firm tops may also use a spring system.