The answer is that it's a single-player game, and that user interfaces suck to write and model. In a multiplayer game you are generally forced to separate game

The answer is that it's a single-player game, and that user interfaces suck to write and model. In a multiplayer game you are generally forced to separate game logic from the UI frontend, which is a good practice regardless. But in a single-player game there is nothing forcing you to do so, and it can be (at least in the short term) very convenient to tie in game logic with the user interface code, as seemingly they follow the same state machine. But then new requirements pop up, such as being able to go back to review your choice, or weird slowness/strangeness that allows you to quickly press a button twice, etc.