There's a shop that serves pudding. They serve two flavors: butterscotch and chocolate. They don't ask what flavor anybody wants, because they think they already know. Everyone's preferred flavor is assigned at birth, and it's even written on everyone's driver's license and/or other forms of ID. Usually, this works out. Almost everybody is content to enjoy their assigned pudding flavor for their whole lives.
A few people don't like the flavor they have been assigned. Technically they are free to switch to the other flavor, but it can be difficult because the shop is stubborn. They just serve you the pudding flavor they think you always wanted, and it can take some effort to convince them they were getting it wrong. Some of these people, rather than switching from chocolate to butterscotch or vice versa, actually prefer to mix them, or they might want an unadvertised flavor like french vanilla, or maybe they don't want pudding at all. This is okay too, but it takes extra explaining at t