Yes, dealers also perform service, even beyond warranty items. The mechanics may not make a commission, but they are usually not the people talking directly to customers at a dealership. Instead, they send a "service advisor" that may or may not have any idea about cars. This person's job is to make money for the dealership and it isn't uncommon for their compensation to be commission based.
There are conflicts of interest everywhere in this process, as you might imagine.
the split between service reps and the actual service department is another reason I don't like having service done at the dealer, it's annoying having the service rep have a hard time interpreting notes written by the mechanic that worked on it, when at an independent shop you'd just talk to the mechanic.
But most dealerships are set up with a "service bay" that's just the desks of the service reps and a couple of parking spots, then after you leave they drive the cars around back to the actual service department. There's total isolation between the customers and the people doing the work. I suspect they might consider this a feature, "white glove service" or something, but it's irritating when you e.g. bring something in for diagnostics, and then get the diagnostic report from someone who doesn't understand half of it - an experience I have had repeatedly taking my lemon of a Nissan to the Nissan dealership because no one else in town has the stupid Nissan proprietary diagnostic computer.
Seriously, when I brought it in to have them figure out a problem that had been frustrating me for a while (I do most of the work on my cars myself), they confirmed my suspicion that it was the fuel pump and maybe saved me the work of replacing the fuel pump when it wasn't the problem. But, the service advisor also told me they recommended replacing the entire steering rack (!). When I asked why, he seriously struggled to come up with an answer, and just said something about it being worn. Really? the quoted rate on the replacement was more than the car was worth, and he didn't even know why they were recommending it.
Now I think I need a stability control reset that as far as I can tell only the dealership can do. I've really been avoiding bringing it in as I know they're going to charge me at least their $170 diagnostic rate and probably write me a quote for over $8k in work again, all for something that apparently takes about 30 seconds if you happen to have a Nissan CONSULT II.
I've had nothing but good experience with my Honda/Acura dealer. The rep/mechanic relationship is just like the waiter/cook relationship. It saves the mechanics' time so they don't have to deal with billing and explaining stuff.
At the same time, I've had no problem asking to go directly into the shop and talking to mechanic while pointing at the part in question.
There you go - I trusted the Honda part of my dealer, but my Honda had a bunch of problems under warranty, didn't cost me, but made me ask why not drive something more interesting, and there were BMW, Mercedes, and Mini under the same ownership, next door. So I thought, eh, the difference in reliability is exaggerated, I'll get a used German car for peanuts, considering the extreme depreciation, and be dealing with the same people. I don't regret buying an out-of-warranty car (yet), but I didn't realize that once they assessed me as someone who makes poor decisions/is reckless/has too much money that they would not treat me the same as with the Honda. Or maybe it's just separate management.
So I conclude, as everyone says, you got to do your own work as much as possible on an out of warranty European car.
There are conflicts of interest everywhere in this process, as you might imagine.