When I first started working at Observable I explained reactivity to my now-wife as “when one thing changes, other things that depend on it update automatically.” She was at an asset management job at the time working in Excel all day, which of course is also reactive in that sense. But she interpreted my statement differently; she said “Oh that’s terrible! If a number changes I want to know.” E.g. if the estimated budget for a project had ballooned, she wanted to hear about it so she could check why, ask other people about it, try to contain the damage, warn others, make other decisions differently, etc. “Automatic” would be harmful, like in your Go example. She was also thinking about coarser-grained data than I was — a single very impactful number, not a stream of mousemoves or pageloads or ad clicks or whatever.