An interruption costs far more than it takes

The thirty second question is not a thirty second event.

Someone asks you something brief. You answer, they go, and the whole exchange takes under a minute. Nothing on any ledger records a loss. But the thing you were holding in your head when they arrived is now partly gone, and getting back to where you were is not instant. The visible cost was the exchange. The actual cost was the rebuilding, and the rebuilding never gets attributed to the interruption that caused it.

This is why open access to your attention is expensive in a way that is very hard to argue about. Each individual interruption is defensible. Each one is short, reasonable and often genuinely useful to whoever initiated it. It is only in aggregate, across a day of them, that the effect becomes obvious: a person who was available to everybody all day and unable to do the one thing that actually required them.

The uncomfortable part is that this makes availability a real trade rather than a free virtue. Being reachable is worth something. So is being able to finish a difficult thing. You cannot maximise both, and pretending otherwise usually resolves quietly in favour of availability, because availability has people asking for it and depth has only you.