Making a fun game is hard. Making a fun game that people can easily get into yet stay forever in? Impossible. Crafting a good and interactive tutorial then slowly letting more and more slack out to the player is a very fine balancing act. Many games are known for their steep learning curves, but resilient and patient players are usually rewarded with a very good game.
At some times, it feels as if a developer doesn't know how to explain a simple function to an otherwise ignorant player. To the dev, its an obvious route, considering that he or she coded it, tested it, debugged, tested, debugged again, then finally got it to work. However the player will always follow the path of least resistance, and / or the logical path.
Getting a player to think in a non-puzzle format is hard, because instead of looking at the problem critically, a player will simply think he is missing something from his inventory or hasn't picked up a quest somewhere. Sometimes, it seems as if the game is broken, and progression is impossible.
However a game's intuitiveness is key. If a player can easily figure out what to do without exactly being told, then a good amount of thought has been put into how people gain their information from the game.
So what makes a game intuitive, easy to use? Some standards have already been set out for each genre. If you see a '!' over an NPC's head in an RPG, they most likely have a quest available for you. Each game has its own 'tell' that signifies something. And figuring out what they mean is the problem. Most games outline these in the instruction manual.
The best thing, arguably, is simply a clear, concise tutorial. Reading the instruction manual versus the tutorial is akin to reading a recipe or making food.