As Glenfer says, Steam is not the best choice you could make. You could have easily found the answer here before, as there are many posts about the topic.
That being said, what you mention is not a bug, and doesn't have anything to do with Steam.
Creating an airport takes a huge amount of work, adding 3D buildings to it takes even more time and it has not always been possible.
Laminar Research is a small team and they made the choice to focus on programming, developing the rendering machine, the physical model etc... you can read a lot about it. They also made the choice to provide a very good documentation and very good tools, so that users can improve the "data content" of the simulator.
You can take a look at the scenery gateway to get a greater picture of all the work that is being done by volunteer developers/users (I am one of them and we are nearly 3000 just for improving default airports). On that web site, you will be able to follow this work and you will find out that 1 out of 5 airports in X-plane, has 3D buildings in it.
You will also see that an average of 10 airports are upgraded every day.
Another good news : it will be possible, in a matter of weeks, to upload airports with ground traffic. And this is thanks to the huge amount of work provided by Laminar Research team.
So if you want to browse the scenery gateway, here is the link :
All the best to you :)