The problem is that real life, while fascinating and gut-wrenching tends to linger in the dull bits longer than we'd like. A filmmaker's job is to make the best film possible, and sacrificing a few facts on the alter of public appeal is to be expected. What's not expected is the degree to which movies lie to us. An extreme example would be Fargo, which purports to be based on a true story, but is in fact almost completely fabricated.
Or take Braveheart, Mel Gibson's gritty biopic of the Scottish folk hero William Wallace. The list of historical inaccuracies is long and detailed, but I'll give you some highlights. Some are mundane: Kilts didn't enter Scottish fashion until about 500 years after the movie takes place. Wallace was far wealthier than depicted in the film. His lover's name, according to legend, was "Marion", not "Murron". Some are a bit more important: Wallace did not invent schiltrons. The Battle of Stirling Bridge actually took place on (as the name implies) a bridge. And it's utterly impossible for Wallace to have cuckolded Edward II, since he died some six years before Edward married. And lastly, there's the downright baffling: the exclusion of Andrew de Morray, the sacking of York (which never happened), and exclusion of the Battle of Bannockburn, or the fact that the nickname "Braveheart" was actually given to Robert the Bruce.
Even documentaries lie to us. Michael Moore, who popularized the documentary as a political and dramatic medium in the 90's, is renowned for playing fast-and-loose with the facts. His first film, Roger & Me alters the sequence of events to make his argument seem stronger. One scene famously depicts Moore being ignored at a shareholders meeting, when in fact he spliced footage from the meeting together with footage of himself on a sound stage. The opening of Bowling For Columbine was almost completely staged--the bank that gives away guns never keeps guns on the premises (the "vault" mentioned in the film was some 300 miles away) and only did so for the film because they had been misled about the subject of the movie. It's a small wonder that Moore's question "don't you think it's kind of dangerous handing out guns at a bank?" isn't answered--the shot immediately cuts off.
None of this is all that surprising. Arguably it's not even wrong (in Moore's case, you can make the argument that he suspends momentary truth in search of a greater truth--I don't buy it, but you can make that argument). The problem is that so much of our knowledge of the world comes by way of our televisions. How much has COPS informed our understanding of crime? Or how badly have the CSI offshoots distorted our understanding of what a crime lab does?
If we don't understand that world, how can we live in it responsibly? And if we're constantly being misled about the way it works, how can we ever hope to understand it?
Not to be a realism junkie, but some things are more important than entertainment value.