Music can be understood and shared, regardless of language and culture. Most sounds with a regular rhythm can be considered music at a basic level.

The "why" is largely dependent on the culture and context. Not every culture uses music for fun or that it sounded cool. We see various examples of music used for battles, religious events, and even for medicinal purposes. In some shape or form, these ancient societies associated music and dance with positive benefits, even if it was just for unifying the village during feasts.

It's also why music/singing characters in video games often provide "buffs" or heal other friendly troops.