They are there to use in pieces of art not there to be part of a brush pack. There is a big difference. When you use someone elses work in a brush pack what did you actually make? I mean using the marquee tool with a feather on it doesnt actually constitute doing something.
Have you ever made a brush pack? Because if you did you would know the time and effort put into them. The hardest part to making a brush pack is finding a render that will work with it, so far I have only found a few and had to google some. Brush making is harder than you think.