Guys like Finn Balor or Tyler Breeze not being on 205 even for the occasional one-off storyline is all the proof you need that they look at it as a demotion for main roster cats. Finn is still Triple H's guy, so he's viewed as too valuable for the Crusierweights.
Shame that's the case. We already saw what adding Enzo did for 205. Imagine if they could replicate that with people who can actually wrestle.