Maintenance renewals are lost one extra click at a time
The maintenance visitor is not in a hurry, but they are also not motivated. That is the combination that kills booking rates.
A maintenance plan customer coming back to rebook a tune-up is a warm visit that should convert nearly every time. Instead most of them drop out quietly, because the booking path requires an account, or a login they forgot, or a form that asks for their system details they would have to go and find, or simply takes long enough that they close the tab and mean to come back.
Unlike a missed emergency call, a lapsed maintenance renewal generates no complaint and no record. Nobody called. Nothing happened. The customer does not think of themselves as having left, and the company does not know they have. It shows up months later as a shorter list, and the root cause never gets diagnosed because nothing went wrong in an obvious way.
The fix is a booking path that takes one step for a returning customer and two at most for a new one. If you have a maintenance plan, the link to book a visit should be the second most prominent thing on the page after the emergency route. Most sites bury it in a footer or require a login to a customer portal most people cannot remember.