What is the in lore reason they didn't force Riker to promote after Best of Both Worlds?
Listen, I get it. The show is the show. We have to keep the cast together. Now that I've said that...
This canon test is decades old but from what I remember they lost 39 ships and 10k personnel (sidenote: do I remember Sisko escaping with Jake in a recap episode? Why didn't the effing Admiral get everyone off these ships that wasn't actual Starfleet? Surely they could have spared runabouts or a few dozen shuttle craft with warp capabilities to get these people away from an active battle zone if they couldn't spare a ship).
First answer what I THINK would/should have happened: Picard would be promoted to Admiral soon thereafter, maybe within 6 months post the episode with his brother (Home?). And Riker's field commission would become permeant almost immediately. I mean this fucking crew saved the damn quadrant, not just Earth.
Lore answer and the only one that makes any effing sense to me: Starfleet promotion system is not externally set but rather self-deterministic. They asked Riker what he wanted to do and he was like "Hang out with Picard and all my buddies on the Ent-D. Why would I leave?"
He was debating promotion in BoBW part 1 anyway. Okay, so they don't have any ships for him for a few months because the fleet is getting rebuilt? Fine. But certainly if Picard wants to stay on the Enterprise then Riker would have carte blanche regarding his ship posting, and specifically being a captain.
The last time we see the crew is in Nemesis, over a decade after the events of these two episodes. And Riker is still first officer, for that matter the rest of the crew is exactly the same. I would think they would get a reputation for being lazy.