A sleeping bag liner makes sense for people who want one lightweight item that can cover several overnight situations. It helps on camping trips, hostel stays, guest visits, and last-minute plans where you want a cleaner and more comfortable layer without packing full bedding.
For apartments, frequent travel, and emergency overnight kits, the value comes from portability and simplicity. A liner stores easily, washes quickly, and gives you a reusable sleep layer that is ready whenever plans become less predictable.