I have never bought a car from a dealer as I always found a better deal privately. But I do agree, as a business, if you're dodgy-ing up your work, you don't deserve to be in business. For the uninformed, this usually kills the reputation of the car. This is why everyone thinks BNR32 will grenade its motor if you floor it once. Dodgy car, unknown history, bought from dodgy yard/person.
My relatively rough car has been going great for what it is. I bought it knowing it had issues, still doesn't stop me from enjoying it (stupid HICAS and AFMs).