why do many nightclubs in US choose Flier as their number one marketing strategy?

[Matthew]

I am graphics designer, and I have a lot of clients in different states, most of them use flier to market their clubs or their events, I just wondering why they don't use other form of strategy?above are my sample works:

http://www.onedaygraphics.com/

http://www.facebook.com/onedaygraphics?fref=ts

[Whats Up Doc]

They are slowly going that way.It takes time for new concepts to take hold.