The beings in question are human-sized that instinctively build nests when they are ready to have kids. The nests are similar to a drey but with the opening on top, like a bird's nest, and are roughly the size of a bed. Naturally, they are used as cribs once the babies are born, and are used while trying to conceive beforehand. They are naturally built in sheltered places on the ground (under a tree, for example). They can also use and create technology like humans. Would their use of technology affect their nests, and if so how would the nests be different?
Instinctual behavior is bad for smart. Birds that are precocial and know to do things as soon as they are hatched are dumber than those that are born helpless.
Your beings would have evolved a culture of nest building, which is very conservative because your bright idea might kill your baby. Still, it will develop with two main pressures: less labor, however you measure it, and works better.
Permanent structures are build once, use many times, which allows you to,preserve good ideas and not pay/build again, as long as basic sanitation measure are feasible. Furthermore, sheltered locations can be built and not just looked for.
Probably as soon as specialists are feasible, there will be nest builders and nest cleaners. In the early days, this might even be a magical or religious role, to protect the young.