Many people first hear about sleeping bag liners through camping, but their best uses go far beyond the trail. They can work in hostels, on overnight trains, in guest rooms, at cabins, and during emergency stays when you want a personal sleep layer that is easy to carry.
That flexibility is what makes a liner worth keeping around. It is one of those simple travel items that can move between outdoor use, everyday backup use, and longer trips without asking for much storage space at home.