Question

why do we only live on earth?

Answer 1

This is because it is not possible to travel to other planets through current technology; even if this was possible, the planet must be inhabitable; there must be drinking water, breathable air, suitable terrain, and several other conditions needed.

Earth is the only planet known so far that is inhabitable by humans.

Answer 2

Earth is the only plabet where life is available. It's the only planet which has water and air,that enables plants to grow to which food is provided.