Question

why do we reproduce ?

Answer 1

Reproduction is needed for the organism to produce its offspring. If we did not reproduce,( the number of people will be decreased). So reproducing is the also important thing for us.
Hope this helps you!

Answer 2

We ( all the animal species ) reproduce to keep the generations alive. Think what would happen if everyone just simply died : the animal race will come to an extinction.

This it is necessary not to get extinct and thus to reproduce.