In case you haven’t heard of the popular “cereal bowl” analogy to illustrate why UX isn't UI, I’ll take a moment to review. The field of UX is in a stage where we need to remind ourselves that it isn’t only about the interface, it’s about the whole experience. One popular way of exemplifying this is to talk about a bowl of cereal - you can’t just redesign the spoon in isolation, you have to consider the spoon, cereal, and bowl as a whole to really understand the experience.
True, but I would argue that this is still too narrow.
What time of day do your users eat cereal? Are there people around them? Are they listening to music? Is it dark or light outside? Is the table high or low? Is there another bowl of cereal on the table? Is it bigger than theirs? How do they feel about that?
Of course UX isn’t just UI. By now, this should be a given. But UX also isn’t just the object (or composition of objects) in isolation. The experience is spatial, temporal, and social as well. If a woman is often interrupted during her morning cereal, how is that different from getting through the meal in peace? Maybe her partner always uses the bigger bowl, and silly as it seems, it kind of irritates her to see that next to her smaller bowl.
These are the things that people experience while they are using your product or service. Sure, you didn’t create these elements, but they certainly affect the way users perceive what you have built. Designing without considering these factors really only addresses a part of the picture that could make or break what you have to offer. Yes, it makes the research and the design more nuanced and complex, but we are dealing with people here: nuanced and complex.
I'll venture an educated guess that if someone is going to switch to a new cereal brand or throw out that bowl, it's probably not solely because their spoon was too small. It’s time to indulge the true complexity of experience, and create smart and traceable designs.