What's the analogy for maxing my manifest?
And what's the analogy for playing the game to have fun?
The café analogy doesn't work for me. Eating is a need, playing is a pastime. The random unlocks give a sense of progression and allow you new toys or skills to bring to your next game. It's typical RPG, in a way: You start out with the basic stuff, but with time new, often improved, possibilities open up. Comparing the experience of playing a game with buying food at a café isn't all that fitting, in my opinion. It's more like you're sitting there for half a day while the waiter brings you random tidbits for you to taste. Some of it's good, some of it surprises you, some of it you politely put away again. Meanwhile, there's two customers in the corner who are paying for a specific meal, which is the reason you're able to sit around and taste small meals free of charge.
Not perfect, but still better (for me) than what Fidite Nemini described. Just different perspectives, I suppose.