==It might be the case that, in general, people can never consider the downsides without leaving the rules in place forever. ==
This assumes that the rules created themselves out of thin air and we never lived without them. In most cases, existing rules/regulations were created in response to events that proved their necessity.
That regulations were created in response to events that should have been regulated does not imply that the resulting legislation was an appropriate way to solve the problem. For example: https://en.wikipedia.org/wiki/Onion_Futures_Act
This assumes that the rules created themselves out of thin air and we never lived without them. In most cases, existing rules/regulations were created in response to events that proved their necessity.