Very large vehicles that are used for bulk transport over long distances often have smaller auxiliary vehicles that they take with them, to allow crew to move around shorter distances easily when at their various destinations. So it makes sense to include such vehicles when you allow heroes to have a large vehicle.
Of course, making sense is not necessarily a guarantee.
Commentary by memnarch (who has not seen the movie)
A generic sci-fi looking building thing to get a looking-around-a-corner shot; sure, why not? Though a moon/planet is a stupid large thing to try and surveil everywhere all the time, the trio here is not being very sneaky while they're heading up to this structure. Unless Finn is somehow actually giving good directions on sneaking in, I think they've probably all been noticed in some capacity by now.
I'm rather surprised the GM didn't make Zeppo and Finn roll against exposure here. Neither of them appear to be dressed for the weather, or even wearing a hat of some kind! Is this not actually snow or something? Keeping a snow layer with no signs of melt like this means it's pretty cold out, and that doesn't even consider the wind chill! At least Chewie's always prepared for the cold.
GM: What are Finn, Zeppo, and Chewie doing?
Finn: We head for the nearest structure.
GM: Okay. It’s about half an hour’s walk across the snow.
Chewbacca: When next we get a chance, Zeppo, I suggest we pick up some hoverbikes to stow in the Falcon.
GM: You reach the small outbuilding.
Finn: Damn. It’s the outhouse.
GM: I said outbuilding...
Zeppo: An outhouse? That’s clever!
Chewbacca: Uh... How so?
Zeppo: It would discourage the workers from taking breaks, having to trek through the snow to get here.
Finn: Exactly! The back door is up on that ridge.
Zeppo: That must be another two hours’ hike.
Finn: Kylo Ren is a cruel taskmaster.
GM: Do you folks even need me to make life difficult for you?