Why a record beats a memory
A damage claim gets decided on evidence, not on how sure you are of what happened. The host who can produce a dated, organized record of the property's condition before a guest arrived starts that conversation from a completely different position than the host who's reconstructing it from memory afterward.
Photos aren't automatically a record
Most hosts do take some photos between guests. Few take them the same way every time, store them anywhere retrievable, or timestamp them in a way that holds up. A stack of unsorted phone photos and an organized pre-stay record solve different problems.
Why it gets skipped during turnover
Turnover time is already tight: cleaning, restocking, resetting for the next guest. Documentation is the first thing to get dropped when the schedule is compressed, precisely because nothing goes wrong most of the time. Until the one time it does.