Nothing’s wrong with Viewmate. I use it from time to time.
But not everyone a) has it, b) is willing and able to download and install it, or c) will register with a company that wants to sell them stuff to get it. It may also be a little too complicated for people that just need a WYSIWYG picture of the content of their files.
I like the circuitpeople solution for the simplicity of it: post a file, look at the contents, and download the images if you need them.