Some people do. It has to do with the "flow" of the subject, like reading from left to right. Various subject "flows" are more appealing going from left to right because of our mind set. Sometimes the "heavy" side will look or feel better to the viewer when it is on the left side of the image. Things like downhill to the right is more "comfortable". Now obviously you don't want to flip images with text in them.

Some people will NOT flip because flipped is not reality. Of course flipping an image is a personal choice and opinion. Try it on some of your images, see if you like the flipped version more.

Below are some images that you can compare by mousing over them to see how each look flipped. The "reality" is the un-flipped version. This might give you something to think about for your images. Not everything may be more appealing if flipped.