Couple of reasons that people hang meat.
Long muscle and fiber will constrict to some extent after a kill. Waiting until it relaxes again improves the texture/tenderness. It should be completely soft again in less than 72 hours.
Ageing meat is a different deal. Done to enhance flavor and is much more to the individual's preference (although additional softening occurs during ageing also). Some people will age meat for quite a while.
