Who has the time for a nice 30 minute game anymore?
Being a titled player does not mean that all of your income comes from chess and that you live a life of luxury (If only! :P). Most titled players have jobs, families, or other endeavors to deal with on a daily basis. As such, it is nice to sneak in a few quick games when there is time to play. This is why it is popular, because it is easy to use no more than 6 minutes to play a quick 3 0 game and then be on your way.
Why play one when you can play many?
More than that though is the appeal to play a larger amount of games and positions. Playing one game which takes many hours has its place and is great for your chess (I think slow chess makes my Blitz better), but it is still only one opening that was played. In an hour, it is possible to play up to 10 openings by playing 10 3 0 games. Or, if you are feeling in the mood for a good sprint, 30 1 0 games.
It is also nice to build those natural reactions. When you play those 10 games in an hour, or perhaps in a week 100 games, then you begin to see positions that can be transposed into, or certain weaknesses in the opponent's position out of experience rather than a keen observation.