I feel like the NXT titles/champions don't generally appear on Raw or Smackdown, whereas most of the ROH title holders, plus a few CMLL and NJPW title holders do appear on AEW quite frequently. If we being real, I think we typically see more title belts on a week of AEW programming than you would on a week of WWE programming. Which I'm not using as a slam on AEW, it's just to say that whatever couple extra belts mainline WWE have over mainline AEW are pretty negligible when you factor in the total number of belts in AEW's orbit.