And that reason is so that you can get better pictures. Yes it is as simple as that. With other cameras I have had, I never would have thought to have done anything else other than to turn the camera on, focus and press the shutter button. Since my intense fascination for photography began about a year ago I began to explore the features that are available on my camera. I may not always get breathtaking results but I do discover, from time to time, that changing the setting on the camera to suit the subject can produce a better picture. Here is an example of what changing the setting can do.
This picture was taken with the auto setting. Notice the bluish tint in the snow?
My camera has a setting specifically for taking pictures of snow. I changed it to that for this next one and you'll notice that the snow doesn't look so blue now.
To get the best results from your digital photos the best thing to do would be to learn how to use the full manual setting. But if you're like me, using a point and shoot camera, and not quite able to get great results, at least check out all the possibilities that your camera has to offer you.