Because duh. When Ian Ziering is having a heart to heart with Mark McGrath and there's a guy cranking out a tune on an electric guitar – on the subway – and then Perez Hilton shows up for some reason, a sudden shark attack really doesn't seem that out of the ordinary.
Here's the first clip from Sharknado 2: The Second One. That title is what happens when you hold Twitter contests to name your movie. Was Sharknado 2 Fast 2 Furious considered copyright infringement?