I would like to start this post by wishing you all a happy (somewhat belated) holiday season.
I LOVE SotU! You can print it on one page. You can print it on one small page. You can modify it to be landscape, and clearly split in the middle, so you can print it on both sides and cut it in half and have two even smaller copies. And THEN you can print it smaller! Which I’ve done.
The system itself is easy to remember, easy to look up, easy to use and easy to improvise around. It’s (supposedly) compatible with everything published for any D&D edition. Some rules are omitted (movement, for example), but could be looked up or improvised. (You might need Labyrinth Lord at the table. Your players won’t.)
Also, it’s pulp as heck! No magic using characters, everyone is a fighter/thief (like Conan, for example) and heroes are captured instead of killed. (And they heal off-screen, like in the movies!)
So what’s not to like? My theory is that casual players want three things out of their game (besides fun): easy to remember/look up rules, minimal reading necessary and lots of options. In SotU, you can choose your weapons, armour and name. An experienced player might enjoy the fact that the characters are distinguished by the players instead of the stats. But if you, for example, are playing D&D with pornstars, They might want mechanical differences between the races and roles. I too catch myself developing race and class options for the game (that I’ll publish later).
All in all, if you ever get cornered by a gang of rabid D&D fans, demanding that you run a game for them or die, you should have a tiny copy in your wallet just in case. And a d8, d20 and d12 is all you need.