Sometimes entertaining means more than just a few hours — it can expand to an overnight stay. If you expect visitors on a somewhat regular basis, it's nice to have the space to set up a guest room…
Providing a beautiful and functional space for visitors to sleep is also a form of entertaining because your guest room says a lot about you (believe it or not). Some believe in two twin beds to squeeze in more people while others provide just one. There's no right or wrong and it really depends on what you think you need.
Maybe you need to use the space in a guest room when guests aren't visiting — day beds are an excellent option because they don't take up much space and provide ample room for a desk or craft table. Here are some gorgeous guest rooms to provide inspiration:
Images: As linked above.