The frame number is the thread everything else hangs from. The sale, the registration, the warranty and every workshop hour sit beneath it, or the same bike ends up existing three times in the system, with three different histories.
Used stock is tied-up capital with an expiry date. Showing days in stock per machine keeps a pricing decision out of the realm of instinct, and nothing else does.
Part exchange is a calculation with two signs. Buy-in value, preparation costs and expected resale must appear in one operation, or the margin disappears into a discount.
The workshop sells time. A booking that occupies a lift and a mechanic at once reserves two resources, not one line in a diary.
Parts depend on the model year. A store that does not file by series eventually sells the wrong brake lever and pays for the return.
Registration is an operation with deadlines and other people's signatures in the middle of it. Treating it as a step of its own, with a status and an owner, avoids handing over a bike whose papers are still on a desk at the insurer.