The thing is they try to avoid having the really big matches on TV, part of the reasons the Takeover shows work so well is that they don't overexpose the matches or wrestlers.
There isn't going to be a situation where two wrestlers wrestle on TV, then wrestle on TV again the next week, then wrestle the week after in a tag match, then they wrestle at the PPV and you're supposed to care?
Instead they might be in a tag, or might not be, but will have some promos between them and segments. The actual singles match will be held off til the Takeover show, and that's good.
The important thing to note is they usually do this for most of the matches, not just the big ones. Adding more time to the weekly TV show means you have to give a lot more of the big stars, possibly watering them down in the process, or give a lot more time to some greener people, maybe exposing them in the process. That you don't see Finn or Bayley or Gable/Jordan or Asuka every week helps in the long run as you don't get so used to the sight of them that they become commonplace.
Plus NXT is taped monthly, even adding a half hour to episodes means taping just two episodes takes three hours., so you'd have to tape twice a month, driving up costs a lot.
