2nd reason? They don’t commit to it.
3rd reason? They don’t know what to change or how, thinking that you can remove a swing flaw from a moving motion by simply deciding to.
Let me tell you a little something that the teaching gurus don’t tell you – without completely overhauling your swing, you aren’t going to change anything, and if you don’t make the commitment to see it through, you’re dead in the water to begin with.