People say we won't ever invent time travel, because if we did, we would have met time travellers by now. People also say the world is getting worse, more wars, natural disasters etc.
How do we know the world wasn't even worse, e.g. there were 4 or 5 World Wars, then after all that settled down, what was left of humanity invented time travel to improve history? Maybe the world now has been influenced by time travellers without our knowledge and currently has the best future they can manage.