Because that's about how much funny parts you get. In other words, you have to sit through 1hr 40mins of a stupid story with too many dumb characters to get 5 minutes of funny humor. Folly on you if you believe all those 7-8-9-10 reviews. Even a 10-year old would roll his/her eyes at this boring, shallow, dumb story waiting for a funny moment every 20 minutes. As another reviewer said, how does Hollywood approve this stuff? Amazing how idiotic they believe us moviegoers to be.