Either so that they wouldn't have to carry everything with them or so they could save time once they arrived at a site by not having to make stuff from scratch.

Most of us a are living in a passive state and we think that someone or something will change our life and save us, which is not a healthy mindset to carry around with you.

Earth can probably only carry one billion humans. As long as human populations continue growing, the battle [to save the planet] will be lost.