The biggest effect, I think, was shops, particularly guild shops, that are only open during certain hours. I think they wanted to have shops that opened and closed, and for whole days to go by within the course of a single session (so you could easily see the environments at different times of day, like sunrise and set, without playing absurd hours). They probably figured that people wouldn't like it if you had to wait really long periods of time just to buy something or see a certain environmental effect.
