1. They usually require you to re-spin the article- waste of time
2. They submit to many worthless article directories
3. They are expensive
There are a few other reasons, but those are my main complaints.
This is how I do my article submission, and honestly with a little practice it takes very little time to do it.
1. Open up 5 windows of your preferred web browser
2. Open 10 tabs in each window
3. Log into 50 of your favorite article directories
4. Submit away!
Of course it does take some time to register for each directory, but you only have to do it once.
Once you do this a few times submitting multiple articles to 50 directories goes by quicker then you might think.