Exactly, my question was basically that: what scenarios are there that we need the logging to expand, that can't be expanded at the call site? The usual ones ar

Exactly, my question was basically that: what scenarios are there that we need the logging to expand, that can't be expanded at the call site? The usual ones are e.g. the date and time (which are popularly set in some logging pattern like %date %loglevel %message). But beyond that, why would I need the logging infra to expand anything in the message portion?