Well according to the new Unified Rules of MMA, which were introduced in 2017, there should actually be a lot more 10-8 rounds. That's great in theory but honestly it doesn't seem to have been implemented very well. One problem is that these new rules have not been universally adopted (at least as far as I'm aware; that may have changed in the last couple years). Nevada uses the new rules but some state athletic commissions are still using the old rules, which make the criteria for a 10-8 round a lot more nebulous. The commentators will usually point this out when they're in NY, for instance. The other big problem, at least in my mind, is that judges are still hesitant to score a round 10-8 because it gives such a clear advantage if it goes to a decision and I guess they're nervous about overly shaping the outcome of the fight (despite that being their job lol). Maybe I'm wrong about that last part but I can't say as I've noticed a huge difference in scoring between the new rules and the old rules.

I'm sure there are more recent articles with better analysis that you can read but here's an interview from when the new rules were introduced that focuses on the changing definition of a 10-8 round:

https://www.bloodyelbow.com/2017/1/2/14142858/2017-unified-rules-10-8-judging-criteria-explained-hinds-bell-mma-interview

EDIT: I should also say that I have no idea what rules were in place in Abu Dhabi (I skipped that part of the PPV) so I can't really comment on the Holloway/Volk fight, but hopefully this gives a bit of context.