Yes, physical intimacy/connection with another

16

Two-pronged answer here. Historically, evolutionarily, it's procreation, which is promoted and encouraged through orgasm, full stop. Socially/ societally, in modern contexts (how we value it now), it's enjoyment, casually or otherwise, and oftentimes at least partially because of orgasm.

5

can be either procreation or just a sociality thing or both

4

Biologically, for procreation. Mentally/physically, depends

3

Sex is inherently at its core meant for reproduction.

1