Difference between Dark/Black Stars, Dark Matter and black holes?

I am having a terrible time understanding or accepting Dark Matter or Black Holes over Dark/Black-Stars. Why are scientists hunting for dark matter to account for the added mass in the galaxies when this could be perfectly explained by darkstars or black stars? A star so massive that its escape velocity is bigger than the speed of light? Couldnt these stars not be detectable by our instruments and account for the added mass in the galaxies? What eliminates these objects from existing in the universe? Also...why are blackholes so widely accepted but dark/black stars are not? Black holes form from a dying star...dark/black stars are just super massive stars approx 485 times the size of our sun?