Castor oil has vitamins for hair growth so it works if it's used as a scalp treatment. My hair has been growing beautifully since I started using it. I agree that it's kind of sticky, but I mix my castor oil with coconut oil to dilute it. It works better that way.
I don't use castor oil on my ends, I use coconut oil on the ends. If castor oil is used just on the ends, it's not as effective.