Even if you don't think it's true that "spawning" is an achievement in and of itself, I think it benefits you that others do "spawn". If you society discouraged

Even if you don't think it's true that "spawning" is an achievement in and of itself, I think it benefits you that others do "spawn". If you society discouraged having children strongly enough, it would collapse. An aged population with no workers or innovators isn't a recipe for success. This is a literal response to your question as to why it's good that people think reproducing is an achievement, I'm not talking about whether it actually is or isn't.