That provides no benefits over a raze/resettle or a puppet and some forethought (having the workboat already there). This is not a question of whether an annex yields benefits, it's a question of whether an annex can yield more benefits compared to the alternatives
Suppose the following case from my last game:
- You have just wasted the second opponent. It is somewhere between turn 65 and 70. You have had The Wheel for about ten turns, and the road network leading out to your new possessions is incomplete.
- You have taken London and York. They are somewhere between fifteen and twenty-five tiles from the capital. Much of it is Rough.
- You have a bunch of terrain that the AI has developed that you cannot currently work due to insufficient pop.
- You have a Whales in London's radius. London and York are your only possessions on this coast; both are coastal.
It's pretty much a no-brainer in this situation to annex the better production site. Developed land > undeveloped land, especially post-Rationalism, and the lost time moving Settlers out there is prohibitively costly. You're better off bringing the territory online now and wasting the time/coin on the Courthouse and the 200G on the Work Boat, as compared to raze/resettling or leaving the territory fallow.
Bringing a Settler with your invasion force is faster. You don't need to wait for the revolt to end.
You could have dropped that Settler and started the Colosseum eight or ten turns ago. If you run a pure Warrior rush, then continually upgrade and attack, your armies will be a very long way from home very early on. Eventually you get the infrastructure to support raze/resettle, but in the first 80 turns it just isn't happening.
The new site produces what, 5-10 or so more base hammers than your next best production city? It takes a very long time for that to be a net positive after building the courthouse. If you ignore the courthouse, that's one hell of a happiness hit, even for a size-10 city (5 + 1.34 * 10 = -18 unhappy) If you are playing for the long term, a raze/resettle will be a better option.
If you rush a Factory in as the first thing you do, 10 base Hammers becomes 15. That gets another multiplier if Railroads are in the game, and still another if you're building Spaceship parts. It can be worthwhile to curtail your expansion as the number of turns remaining diminishes and take a mild Science hit to get a large Hammer increase.
That's not a reason to annex your conquest, only to puppet.
Yes, but the above may be reasons that you wish to annex the conquest at a later date.