The job ticket is the workshop. What is wrong, what was agreed, what it will cost and what it is waiting for: a bike hanging up with no visible status is one nobody dares to phone the owner about.
Parts come from several suppliers on different schedules. Knowing what has been ordered, from whom and when it is due is what turns a vague soon into a date the customer can plan around.
History belongs to the bike. What was replaced and when means the next service starts from knowledge rather than from an inspection, and it makes an honest recommendation possible instead of a guess.
The season has to be measured to be staffed. Knowing how many jobs came through in each week last spring is what decides whether to take on help in March or to turn work away.