I understand what you are saying but Cody just won his belt a few months ago and is taping for the next season of TUF, so that puts the belt on a shelf until TUF ends.
Max and Aldo like Cody got their belts rather recently.
There is always at least a 6 month gap in a title defense. DC got injured a couple times.
The reason people give Conor flak for not defending the belt is because he has just held on the featherweight belt and instead of defending it, he fought Diaz twice, then fought for the lightweight belt. That's chances to defend the featherweight belt.
He gave up the lightweight belt after winning it, so he's good there. Nobody can say "oh no title defense by Conor in lightweight"