A lot of cultures will have raised beds that allow for airflow in hot weather- like the Indian charpoy, the West African stick bed or hammocks.
Other cultures aim to retain heat. The Chinese kang bed is elevated to allow for a clever heating system that allows heat generated from cooking to heat the bed. The kang, FWIW, also serves as a sitting and dining area- truly the center of household activities. During the cold winters, it may be the only truly comfortable part of the house. Some European countries have a tradition of fully-enclosed, cabinet style beds.
But plenty of people have no real need for raised beds, and are happy on mats (which, when placed on deep, clean gravel, can be quite comfortable) or futons. I think it’s really just a matter of cultural preference- is the bed going to be just for sleeping, or do people perform daily activities on it? Does it need to be portable? How many people share a sleeping space?