In X-Men: Days of Future Past, Kitty Pryde can send people's minds back in time to their younger selves. Because of the strain this puts on the mind, she can only send most people back a few days at most. When she needs to send someone back 50 years, that limits her options to Professor Xavier and Wolverine, whose powers can protect them from any negative effects.
Xavier says that he can't help, because he didn't have his powers in 1973, so Wolverine is sent.
However, we later learn that the medication he was taking to enable him to use his legs suppressed his mutant abilities. When he stops taking it his powers return fairly quickly, to the point that he is even able to communicate with his future self through Wolverine's mind.
So, couldn't old Xavier have gone back in time, stopped taking the medication, and then fixed things? Besides giving Wolverine more screentime, is there a reason for this?