Which strikes me as a reflection of the particular state of affairs in the alternate reality, where Starfleet seems to have adopted more of a defense-oriented footing in the wake of the Kelvin's destruction. Perhaps it's only now that the pendulum has shifted back toward Starfleet's exploratory responsibilities. If so, that doesn't reveal anything about the state of affairs in the Prime reality.
I don't know Kirk in TMP seemed to think the 5 year mission was a big deal seeing as that was part of his justification for taking back command of the Enterprise, so it kind of implies not everyone was doing those.
Besides the Enterprise was still probably doing the usual TOS things judging by the star of Into Darkness, they just went back to Earth after finishing up instead of going to the next random planet.
Honestly I'm starting to wonder if a 5 year mission just means running from planet to planet with occasional stops at starbases for 5 years where as regular missions are going to the planet conducting the mission and then returning to the ship's home port (which is kind of the impression I got of what the Enterprise was doing in the TOS films).