Some scenes don’t have a horizon or any lines that should obviously be vertical or horizontal, so “straight” becomes an abstract concept anyway. Extreme sports usually have wild angles and shots taken on the side of a mountain probably will not have a flat, horizontal, horizon. Some studio portraits have the subject leaning and twisting a bit to emphasize shape, or to hide fat and wrinkles.
It would help to see some samples of what you have been looking at. For your own photo, if the background is reasonably plain, you can rotate the image and clone in a little at the edges to fill out the new frame instead of cropping.