I'm one of these returning on a regular bases.
I can't stick with the game the entire time, because a lot of its mechanics are a bit annoying and the grind is too harsh IMHO.

But I like the atmosphere of the game, as well as exploring new maps, or buikding up an infrastructure connecting my different bases via roads, bridges etc.
So I'm returning on a regular basis and start spending a couple of weeks in the game till the next break.

And they're the updates of course und therefore the curiosity about what changed.