They were stylistic reboots, not continuity reboots.
Reboot today usually means running over the same stories again with a new cast. That didn't happen in either of these cases. nuTrek is more of what one would expect from a reboot, only with the thin connecting thread of "alternate reality" and prime-spock cameos.
The paradox of reboots is that by running over the original's greatest-hit story beats, it can actually be MORE derivative than simply building on top of the same continuity. The promise of the reboots being a blank slate is rarely realized because the temptation is too great to just repeat what you know worked the first time. But you don't need a reboot to fall prey to repetition, of course (witness The Force Awakens).
The best reboot candidates are for properties that were highly flawed and could benefit from a do-over. For instance, if Disney were to follow-through on remaking The Black Hole.
The larger galactic/political situation post-Nemesis is only the most superficial backdrop for a story. There's more to Trek than feuding Galactic powers.