The cohort moves together. An eight-week course builds week on week, so somebody joining at week five is not a late enrolment but a different experience, and admitting them without saying so damages the group.
Absence is the early warning. Missing the third week is where most people stop coming altogether, and a short message at that point is what keeps somebody in the course they already paid for.
Two payers, two processes. A company buying for twelve staff needs a purchase order, an invoice and an attendance report, while an individual pays once and expects nothing else.
Notes are sensitive by nature. What somebody says in a session about their sleep, their grief or their anxiety is personal information, and storing it in a shared spreadsheet is a problem waiting to happen.