There's already over 30 pages of multiplayer tutorials, covering concepts, a chat room, pong and a real-time game. We can't, and never will be able to, make a dedicated tutorial for every kind of game anyone might ever want to make. Besides, it's better to teach the fundamentals, so you learn how things work and how to build new things yourself, rather than just following recipe-style tutorials.
Honestly, I think there aren't that many people using multiplayer because networking is just fundamentally difficult. You can make all sorts of excuses, but ultimately you are going from one game (which is often hard enough!), to multiple simultaneous games, all with slightly different time offsets, and all of which need to communicate with each other with varying degrees of latency, latency jitter, and bandwidth constraints. It's far more complicated and requires a whole different mental model about how to design it, which can take a long time to get comfortable with.
So yeah, multiplayer is just hard. I warned everyone it would be, but I think hype exceeded reality, and then when everyone realised that actually yes, it is hard, then it ended up with less usage.
You're smart 
ASHLEY. You're really good at making tools. You could make something that would get more use if you needed to. You could make it slightly simpler or make a demo game that shows off many aspects of it. I read all the pages of documentation, and combed over it slowly. Maybe I could do that again, but it just seems like it could be even more developed. I would like to make an app that includes multiplayer support, something as simple as a classic shooter but with 2 or more players. I understand you can't make demos for everything but I wish you could do one more showing off a few of the features, like a multiplayer cooperative experience where users work together toward a common goal (ie. taking down a horde of ships or a boss together.)