I take your point about profit and older vehicles; unfamiliarity, and fear of the unknown, but declining to perform an MOT ?
The situation reminds me of a very good friend of mine who, some years ago, attended a Mercedes Dealership to buy a new Mercedes Benz
They judged the book by its cover, which wasn't presented as well as it might have been that day.
They treated him poorly and he left.
The following day, he visited his local Rolls Royce dealership; and ordered the latest new model.
As a cash customer, he was offered a courtesy car for the duration of the delivery lead-time.
With all the customer specified 'options' the Rolls took some few weeks to be delivered (literally).
His first trip was to the Mercedes Benz dealership where he discretely parked his latest model (RR) obstructing the main entrance.
He was surprised how long it took Reception to request, over the Tannoy, "Would the owner of (registration, not marque) please come to Reception.
I recently went with my life-long to another MB dealership to buy a new MB !
All was going well, the sales person thought, until my friend was reminded of his prior experience at a MB Dealership.
So, due to their short-sightedness, and expectation of appearance, the MB supply chain lost the sale of two new vehicles and the ongoing servicing revenue over several years.
One thing my friend had learned conducting his own business was that "No Revenue delivers No Profit".
So. Rant over.