It makes sense in large European cities because people won't take their car (if they even have one) because transit is more expensive during rush hour, instead

It makes sense in large European cities because people won't take their car (if they even have one) because transit is more expensive during rush hour, instead they will try to adjust the time they use transit. And yeah, to answer GP I had forgotten that London has such a system that makes it quite easy to implement different fares for off-peak travel, I'm more used to places with fixed fares.