First of all, a sofa bed is really that space-saving solution. Besides the fact that a sofa bed is (obviously) a sofa, it also offers the possibility to become a bed. In other words, you have two functions in one piece of furniture!
This immediately solves the problem that you can use the room for multiple purposes. You can use it as a guest room, but also as a reading room, for example!
If you don't have such a big house at all and don't have room for a guest room, then a sofa bed is also ideal
solution! During the day it is just your couch and in the evening you could possibly use it as a guest bed! This way you can still have cozy sleepovers, despite the fact that your home (or living room) is not that big. The guests can then just sleep on your "couch"! And no worries, the sofa bed gives you (and your guest) enough comfort.