Some people take their cars to the dealer for all services. They do this because they value the expertise and depth that the dealers can [sometimes] provide. Other people take their cars to the local quick lube or brake repair shop.
To each his own for car repairs. And so too it should be for any equipment repairs.
You mean the expertise they claim to provide. Dealership mechanics are generally junior mechanics; the really good, highly-experienced mechanics, go work at or start their own independent shops where they get much better pay.
The big reason that you'd want to visit the dealer rather than an independent mechanic is because you really, really, like spending more money than you have to. There's a reason they're called "stealerships".
There are definitely some times when you want to go to the dealer; especially in rural areas, where the local repair shop has a lot of breadth, but not enough depth, to help with hard problems.
From the article:
> A Crain’s Chicago Business article reported that dealers make five times the profit margin off repair than they do off the sale of new equipment.