Well, ONE rational reason is to keep his medical license.
Knowing the NYT, it's a pack of lies. They ALWAYS promote the WRONG side. I find this to be no exception.
He should have just purchased his 'pain relieveing narcotics' off the Internet. Had Rush done this instead of the allegation of 'Doctor Shopping' (notice I said allegation), He wouldn't have given the lonnies on the Left the ammunition they have to instantly discredit him. But alas, soon the DEA will shut this avenue down for those of us that suffer from chronic pain, due to the lowlifes that abuse this.