Yeah there's no technical reason not to at this point, China has it. Just inertia and having to invest in the systems and processes to do it, I guess. It started at like T+14 when you had to mail physical stock certificates around then +7, +5, +3, +2, I'm sure they'll get there eventually. US futures are already settled T+0.

From my limited experience back office software is a legacy clusterfuck and the Ops team has to pick up the phone and call counter-parties on T+1 to unfuck things more often than you'd think, but those are things that could be fixed with better systems if the investment was made.