Simples:
We are talking Nissan - how often to the technicians in main dealers get to service Zeds - once a month maybe? And who will be doing that, not master technicians you can be sure of that.
And then the bill arrives at God knows what per hour charges are levied to cover all the dealers overheads.
So those who set up Indys who have had the Nissan training can be expected to have in depth knowledge and skills of the specialist models and they themselves will be working on the cars and....most importantly, you as the customer gets to discuss the work on your car with that 'expert' before and after. And how many Nissan garages will allow you to watch their work in progress? Those who buy their Nissans to get them from A to B are just concerned their cars are serviced and fall for the argument that you should always have it main dealer serviced.
And then you know it is being road tested by someone who is concerned they have done the work expected, not another bod who has not done the work or dare I say, as we have heard on several occasions, just enjoyed ragging the car because of what it is...
That said, there are some good Nissan dealers out there who do a really god job from feedback we have seen. But sadly they are in the minority.