Buildings were included as an option for players for a few reasons.
As new features, buildings, etc are released, some previous buildings become obsolete with some players' style or area of gameplay. This would allow some reorganization of the area, getting some of the credits back that was spent for something at the time, made sense, but doesn't anymore.
Some players determine the area they're in, or style of play they're hasn't played out the way they wanted it to. But they aren't likely to find that out within the 24 hours we have to refund a building.
The vehicles followed the same concepts, but their changes have been much more dramatic. For example, when I started playing there were very few combined vehicles and two required the player to reach Captain before they were available.
Essentially, it's just another option and incentive for players to get a portion back as they become more proficient in the game, find better or different ways to do things or adjust to changes in the capabilities of the game. This game ins 2018, when I started playing is very different than today in 2022.