It is also very helpful for people who struggle with the English language in general and writing in particular. A free article spinner or paraphrase tool makes it easier for them to get new content with minimal effort. The quality of content created with article rewriter is close to human written content if not equally good. To ensure the quality, you can edit content to fix any errors.
I've ranked websites in the past with spun content, and now they are still on #1 position of google. First year (2014) google found me because my spun was really bad, many paragraphs were just copied and my position drop from #2 to around #20 after a panda update. Later I cleaned all my text with better spun (I didn't buy any article!), my ranking went up again, and with more backlinks I reached #1 and it is still there