Duration is everything. A cut is forty minutes and a full head of highlights is three hours; a diary that treats them the same either wastes half a day or runs an hour late from eleven in the morning.
A missed colour appointment is the worst loss in the salon. Three hours cannot be refilled at short notice, which is why deposits on long services matter far more than on a quick cut.
Colour formulas belong to the client, not to the stylist. Written into the record, they survive a stylist leaving; kept in somebody's head, they leave with them and take the client too.
Stock disappears quietly. Colour, developer and retail products used and sold without being counted turn into a gap nobody can explain at the end of the quarter.