Making something that go into space is the actual rocket science. Sure someday there will be other methods to get there but I'm pretty sure that will require something much harder than that.
Building just a fake spaceship takes a lot of effort too, even if you don't have to solve the real hard questions. We are trying to make a school look and feel like a starship! Definitely not an easy task.
Even if we don't need it to actually go into space there things that would be easier if we could actually send it into space. Some problems wouldn't even exist for us. We need to fale many things just to make it feel like that. And that's a lot of extra effort.
An engine of a real spaceship might for example over heat or otherwise malfunction. No spaceship designer need to worry about making that happen. They only need to worry about how to deal with it. With a fake engine we also need to fake those issues and make them happen. Everything also needs to look like a "real" spaceship whereas it doesn't really matter what things look like when you can actually go into space.