The 'mayor' features was the thing to make NL so different than the other games, and it's what set a new standard for the series. They even said in one interview that it made for a great reason to include PWP's, as well as different features (like changing shops closing times and such). As a 'mayor' you are given the power to change those stuff -- so it makes for a reasonable reason within the game as to why you would be able to do that in the first place.