I suppose it depends very much on why the owner has purchased the car as well as his financial situation. I have long since given up servicing my daily driver but I would probably service a vintage car if I had one.
When it comes to the Morgan it is a bit of both. I get one dealer service a year but for the day to day stuff and any adjustments to the throttle bodies or ECU calibration I do that myself. I installed the throttle bodies myself but had Borghi install the suspension components because they have the experience and the equipment for the heavier work.