A dealership or a distributor is not one business. Parts is a stocking and velocity business. Service is a scheduling and labour business. Whole goods is a margin and trade-in business. They share a building, a phone number and a general ledger, and they are usually measured as though they were one thing.
The people are rarely the problem. The counter knows which part actually fits, the service manager knows which job will overrun, and the salesperson knows what the trade is really worth. What leaks is everything that depends on those three knowing at the same time: a service job waiting on a part that was never ordered, a warranty claim that aged past the window, and a whole-goods deal priced against a trade-in valued from memory.