Lazy Planet
Once people came up with a way to make themselves immortal, they became completely unmotivated. Why do anything if there's no time limit to do it in? Their buildings fell into disrepair, no one made music anymore, all of them forgot how to ride bikes. Mating turned low-priority too, since there was no rush. They tried watching TV, but it was only reruns, as no one possessed the work ethic to write, direct, act in, or produce anything. The cooking programs just showed people unwrapping fast food. We tried motivating them, but they just blinked at us, so we left.