There are many people who still prefer rewriting their articles by hand. They are used to write sentence after sentence and rephrase their content to ensure the quality of writing. Although it is the safest approach but it can take hours or days to complete a task. On the other hand, there also exist people who are either too lazy to rewrite their content or they understand the importance of time and hence, they look for an article spinner tool or paraphrasing tool.
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