If you're falsely accused of murder, would you call your cousin who was "really smart," and who (you're pretty sure) took some law courses in college? Unless you're a big fan of confined spaces and institutional meals, I'm confident you'll call an experienced attorney with a strong background in criminal law and a solid track record of acquittals, even though he's much more expensive. (Doubly so if you're guilty!)
Of course, nobody's going to die if your wedding photos come out little better than the flood of cell phone images your friends will surely plaster all over Facebook and Instagram. While not quite life or death, it's surely an extremely important and -- if you're lucky -- once-in-a-lifetime event. Hopefully your wedding ring didn't come from Wal-Mart; shouldn't you take the same care in choosing who will create the only permanent record of your special day?
The moments are going to happen anyway -- but they'll often happen in bad light in front of distracting backgrounds. The job of a professional photographer is to pay attention to the details of lighting and backgrounds, so that you don't have to -- and unobtrusively direct and adjust the environment to correct any issues that would make the pictures less than remarkable.
Here, newlyweds talk about the importance of investing in professional photographers because at the end of their big day, their wedding photos were all they had left.