Thoughts/Long Rambling : How to give a good lifespan to simulation games?

[My title got lost in translation, but in my native language there is a term employed for the type of games I mean : "Management games". It's more about city builders, sims or tycoon games than the pure simulation stuff.]

So I was playing at Banished the other day, and once I built all the buildings I could, I couldn't shake a feeling inside of me : it was it, somehow I "beat" the game. Which was not very true : my population was still growing, and I had yet to build several farms to prevent my poeple from starving. But I didn't find it to be as fun as it was in the early game.

Now I'm not posting to burn Banished down, but rather to ask myself - and yourselves - how can we motivate a player to stay engaged on the same city (in city builders, but it can also be farms on farming simulators and so on...) even when he/she got through the "discovering part" of the game.

By "discovering part", I mean the time when the player genuinely "discovers" the actions he can take in a single game. In a game like Banished, the "discovering part" can be over after the player's first game. It is then debattable to say if during his/her second playthrough of Banished (s)he will feel that "discovering part" once again. My first guess is no, since (s)he will already know what (s)he can build and not "discover" it anymore. On the other hand, maybe that, in a game like Banished, which have no clear objectives beside the survival of your population, the major way to feel like the player has beaten the game is to build once all the types of buildings (s)he is able to. Maybe it would be best to separate the "discovering part" of the game with the "I'm yet to beat the game" mentality I last spoke of... But I'm probably rambling here, and not really getting on my point.

So one of the solutions to giving lifespan to a "management game" (for the sake of the argument, let's keep the city builder genre), seems to be creating several maps with objectives attached on them. Old management games from the studio Impressions Games used to do that kind of stuff : Zeus, Emperor, Pharaoh, Ceasar, and it was working, in a way. What kept the player engaged was to achieve his/her current objective, and then get the next (and new) one. If I recall correctly, the story went on beetween each new objective. It's like there was a sense of discovery - like the discovery part I was talking earlier - behind this way of going on in the game. By reaching an objective, you had the satisfaction of beating the game (or atleast a part of the game, but it's satisfaction nonetheless) and satisfaction coming from discovery : The plot (even though this particular genre isn't the best if you're looking for good plots) was going forward, and some missions asked you to build some particular buildings or to do particular things ---> Hence, sense of discovery.

In Zeus, for exemple, the missions were grouped in campaigns. You were building 1 town in each campaign (on some missions, you would build colonies, attached to your first city), and each campaigns had beetween 5 and 12 missions (maybe not the good numbers, but who cares). In the campaigns with 5 missions, every single one of them were pushing you a little, as a player, to build a bit more of your city - usually because you could not build everything on the first missions. Plus, each city on each campaigns had buildings that couldn't be made at all, bringing some uniqueness in each city's requirements and each campaign as a whole. At the end of a 5 missions campaign, you had a nice, medium sized city. At the end of the 12 missions campaign, you had built a majestuous one.

And then you were asked if you would go on with this big city you built. And I usually said no.

I had already spent a lot of time on these cities, so, maybe they had done their time, you know. But the thing is, in Zeus, I never really enjoyed the sandbox maps with 0 objectives. I did enjoy it once, though, because it's the only map in which you can build and have everything in one city. So yeah, I did it once or twice, and then I conquered every other city with the great army I built easily. And that was it. Once I did it, it was like Banished all over again.

Zeus, besides objectives, doesn't have much to bring on the table once you know the game - I'm not blaming it at all, considering the game has around 20 years, now. I sometimes ask myself if I would play it again, and even though I think I could do all the campaigns once again, I certainly would not do the sandbox map anymore. I know what is keeping me on Zeus are the objectives, and I know that what kept me on Banished was the wish of discovery - maybe it's more true to say that the lack of it drove me away.

But now I wonder : What if the craving of new things wasn't the only things tying you to a management game? And if that was the case, what would that other thing be?

I'm kind of stuck because I haven't felt connected to a city-builder (or any other management game) that was not pushing me to discover new things, but if some of you poeple enjoy spending time on 1 particular city/farm/zoo/sims family, why do you do? What drives you to go on with the same thing?

TL;DR : Check the last 2 paragraphs

Thank you for reading me, I'm keeping some thoughts at bay, because I didn't expect my ramblings to take that much space.

PS : Sorry for my english, it is not my native language.