Because I get tired of seeing really shoddy poor or just lazy cropping so often. This is an incredibly simple way of checking to see if you've deleted/cut out/cropped your stock object/image/model properly and takes just a moment to do.
How easier could it be?
This may be shared if you find it useful, but please leave my credit thanks
This can be done in almost every version of photoshop/gimp and more than likely similar in any other drawing package.