Why did Washington choose to retire instead of continuing into a third term in office?

Because he go lazy and did not want to deal with other human beings anymore so he quit

Because he felt like the united states would end up like a republic, very similar to England. The reason that he did not want to become absolute ruler, is because being a commander in the fight against the British, he did not want to be come the very thing that they had fought so hard to get away from.