"Greener pastures" doesn't always mean literally greener pastures. And there are other reasons to go places besides you think it'll be "better" than where you

"Greener pastures" doesn't always mean literally greener pastures. And there are other reasons to go places besides you think it'll be "better" than where you are now: exploration, for example. Scientific curiosity. Adventure. Not everyone that has set out exploring has done so because they thought they'd find a "better" place (which is thoroughly subjective), rather in hopes they'd find a different place. Earth may be the best place for you, but you are not everyone.