It occured to me: According to the building card, the only effect of the most basic racetrack is "allows races to be held". When you upgrade it you would expect that it had some additional effect, for example a bonus to public order to representent that more people can watch more spectacular races. But no, even the Circus Maximus has "allows races to be held" as the only listed effect. Are there any hidden effects of the greater tracks that I am not aware of? If not, what possible reason other than role-playing could there be for building these upgrades?