Netflix has far too much content to list everything in its front end. We're talking about like 100,000 things. The suggestions and categories use their predictive algorithms to list things that are popular, and things that you may like based on your history and ratings. You kind of have to train it to your tastes and it will be better at surfacing things you might like. In that way it's a bit like a music discovery service rather than a comprehensive library. When you're starting out it can be easier to go to the website and delve deeper into all the subcategories, rate a bunch of stuff you've seen and add anything that looks interesting to your instant queue.
Game of Thrones is an HBO show. They do not license their content to anyone for streaming.
