Some indie publishers think just putting their work “out there” is good enough. They wrote the book, proofread it, and they’re done. Buy it. Maybe they hired someone to edit it. Maybe they found a stock image (there’s nothing wrong with stock art, but there’s a time & place for everything) for the cover and put some text over it.
I always buy original art for my covers. I just think it looks better and it lets me show exactly what I want. I designed the cover for Zack Jackson & The Cult of Athos myself and thought it looked pretty good. In retrospect, and this became particularly clear when I tried to use the same style for the second book, it was really amateurish. So, I hired a professional graphic designer. The results speak for themselves (the border is actually squared off in the first cover; WordPress makes the edges round). Zack Jackson & The Cult of Athos has been redesigned to match the new style, as well.