'Based on a true story'

I hate those five words. I really don't understand why filmmakers, writers, and the like feel the need to tell us something like this happened in real life. Specially when everybody knows it didn't. Why? Because real life isn't like a movie, or a TV show, or any piece of entertainment. Real life is complex, even messy. It has a lot of minor characters, uninteresting plot. A lot of the times, lots of unrelated stuff happens out of nowhere. And the endings are a letdown.

Movies, on the other hand, have to be entertaining. It's not that something has to explode every six seconds, but rather, that it has to have a story, a plot. It has to have a certain pace and rhytm. Edits have to be made, and things have to be rewritten. It's no wonder that the end product has little resemblance with the 'real life happening' it is supposedly based upon.

So, what I don't get is the need to try to convince the public that the stuff that we see on the screen has any sort of basis on reality. Isn't the fact that it's an interesting, compelling story enough?