Time travel will never be invented, because someone would have come back to visit and that has never happened.
Why would they come back here? They would go to a time when there was no mass communications to study the places and people, like Ancient Rome or Greece...................
Asimov addressed that in The End of Eternity, where time travel required a field of some sort to be set up, and therefore time travel could not go before the date this field was first set up.
“Time travel will never be invented, because someone would have come back to visit and that has never happened.”
Maybe they just know what idiots we are and don’t want to make contact.
Perhaps the rulz do not allow one to go back before time travel was invented?
Causality shifts/recrystallizes/goes through a phase change from that moment...
Think it was Niven working on the viewpoint that every time someone built a time machine, the Universe found a way of erasing their efforts to avoid a paradox. If your sun goes Nova just as you complete your time machine, you might be having a bad day!