Does everyone know that time travel exists? Or is it like a secret? If there was only one, whoever controlled it either way would be all powerful and immediate ruler of all people on Earth. There’s literally nothing you wouldn’t be able to do, and no force could stop you. Economics would be yours to control.

If everyone had access to time machines, it would be chaos. Markets literally would grind to a halt, because time travelers would be perpetually competing to be 1 second ahead of their competitors, all the way back to the beginning of time. Humanity would inevitably destroy itself.