A reindex is the rebuild you pay after you lose the thread. You sit back down to the thing you were deep in, the context is gone, and before any real work happens you have to reconstruct where you were, what you had decided, and what came next.
Databases do this literally: change enough underneath an index and it must be rebuilt before queries are fast again. Interrupt a focused person and the same bill comes due. The interruption was a minute; the reindex is fifteen.
This is the hidden cost in “got a sec?” The second was never the price. The reindex was. Protecting focus is mostly about not paying this tax forty times a day.