And if you don't do it, then you're not on the map. You're dammed if you do and dammed if you don't. There are may claims by the PR firms that do this. They claim that they're increasing the visitors, the investment, the sales, etc. But the cause and effect isn't there.
Cities change certainly, but whether it is due to the marketing, no one knows.
All advertising is positive, so we take it with a grain of salt, but we're very influenced by it too. Certainly a number of campaigns have improved the self-image of the city, feeling proud of their city, such as Atlanta, Pittsburgh, Cleveland. It is one of the positive aspects of marketing. Examples are heritage landscape and main street programs. Planners are ideally those who take the benefits from marketing.