Why does Gandalf...

[Lord of Angmar]

I cant say Gandalf would have helped that much. How much good did he do in the hobbit? Bad stuff stil happened.

Oh, he would have helped. A being with the power to fight all the Ringwraiths at once would probably have prevented the Nazgul from stabbing Frodo. Frodo's being stabbed by the Witch King, in my opinion, not only hindered their flight to Rivendell but also made Frodo more susceptible to the Ring's power throughout the course of his entire quest.