Most galleries hang the centre of a work at roughly 145–150 centimetres from the floor — a convention derived from average eye height, not aesthetic preference. It's the physical equivalent of a baseline grid: an invisible rule that makes unrelated works, hung by different curators in different decades, feel like they belong to a single coherent system.
Spacing as punctuation
The gap between two works on a gallery wall functions exactly like whitespace between two sections on a webpage: too little, and the works visually collide, competing for attention neither fully wins; too much, and the relationship between them disappears, each work reading as unrelated to its neighbour rather than deliberately placed near it. Curators adjust spacing to control that relationship as precisely as a designer adjusts margin and padding, usually without a visitor ever consciously noticing the decision.
Sequence as a forced narrative
A room hung chronologically tells a different story than the same works hung thematically, even though not one painting has changed. Sequence is an argument laid on top of the objects, exactly the way the order of sections on a landing page argues for a certain reading of a product, using the identical content a different order would present as a completely different pitch.
Nothing on a gallery wall is arbitrary except what visitors are meant to think is arbitrary.
Interface designers who treat spacing and sequence as "just visual polish" are skipping the exact decisions curators treat as the actual argument.