Because the HW division is an unproven division. Cain's biggest wins in his career are jds and lesnar. Jones has beat rashad, rampage, lyoto, vitor, chael, bader, and shogun. Literally everyone that he could possibly beat he did. And to each their own also. When rashad became champ people thought he was just too good. Then machida beat him and people thought he was just too good. Then shogun beat machida and everyone thought he was just too good (bar the knee injury). What im saying is the people jones has beat were all looked at by many people as someone that was going to reign to division for a long time. And not only did he beat them, he completely dominated them.
Literally none of those guys you mention have looked impressive in years, aside from Vitor who is a MW.
While they were once at the level of a JDS, they are not in the prime of their careers like JDS currently is. After Bones beats Glover and Gus i'll give him more credit.
I would be happy to take any bets regarding Cain V Bones when it comes around.