Randomness

Randomness can add character to a game. But you don't want players restarting their turns because of a significant random outcome.

It is fine for players to play for several turns, realise they've made a strategic error and go back to a saved game several turn ago and restart from that point. But to be incentivised to replay a single turn more than once due to the significance of a random outcome would not be satisfying gameplay.

As an example, introducing randomness into technology advancement could only be done if the element that was random was quite minimal, and the significance of the technology more minor.