The people decide what they "want to know," and then journalists go out and try to get it for them. That's the relationship. So as long as people are interested in the rumors of Ryan Mallett's supposed drug use, he'll face questions about it. That's the way the system is set up, and Ryan Mallett has chosen of his own free will to pursue a career in the public eye.
His agents and PR people should have had him better prepared, as there are strategies and word choices he could have used that would have prevented much of this fallout. Admitting to "mistakes," and then not elaborating, for one (which he hasn't done). Saying "these things are in my past." "I think we've all done things we're not proud of." "I'm not a perfect person." Etc etc. That's what you say if at least some of it is true. And if it's not, then you get up there and ****ing deny it.
It's not a matter of "obligation," it's just what you do if you're smart. Pretending as if the issue is just going to go away if you don't answer questions about it doesn't work. And at minimum, the people Mallett has hired to help him through this process should have known that. This whole thing is their failure as much as it's anyone's.
What seems pretty clear to me is that the story -- whatever it is -- is bound to come out eventually. The teams likely have the story already, and whoever talked to them is eventually going to talk to someone in the media. And as the history of these kinds of things have shown, the later it comes out, the worse it's going to be... the more pressure there's going to be on Front Offices to take the guy off their board for fear of a public relations backlash. It's always better if you have control of it, can choose how it comes out, can be there to help form people's opinions before they become concrete.
The worst thing that could happen to Ryan Mallett from a public relations standpoint is for SI to come out with an 8,000 word story a week before the draft confirming everyone and anyone's worst fears about what he's done, with people from his past spinning off stories, real or imagined, that don't match Mallett's version of events.