well, that's because he isn't in those talks. Is he one of the best fighers we have seen? Sure, but his resume isn't the strongest to be honest. He's beat a couple decent HW's, Barnett and Big Foot were solid wins, can even toss in Mir in there or whatever. At LHW, he's beat Gus and Rumble 2x. Volkan who really hasn't proven much maybe you can toss him in. But that's it. Anderson and Hendo at LHW at the time of the fights, although big names, were not really worthy contenders at that weight class. He's never really been dominant. He's not even the 2nd best LHW ever if you actually consider their whole body of work.
does that mean he sucks? No. But it's hard to say you're the greatest of all time when you have never been the best of your own time.