Shuttle is a detailed simulation. Let's look at those words carefully. "Detailed". "Simulation".
We'll start with "simulation". This software is an attempt to simulate the Space Shuttle. Like a flight simulator it tries to accurately recreate that machine in software. You typically get two types of simulators in computer software. The first is the Forza/Gran Turismo type of simulator where, sure, cars and tracks have been measured with lasers to within a micron of their lives, and some people will play them with a steering wheel and pedals, but most will just use a gamepad. And that's fine, because mostly they are just about having fun.