Would you buy a brand of car if you could only get parts and service and maintenance at the dealer’s shop?
People buy Tesla’s. Good luck finding aftermarket parts or repair shops
Aside from maybe routine oil changes and tires, I go to my auto dealership for all major maintenance. Why? Because they have certified factory-trained techs that only work on the brand of car that I have. Because they use genuine OEM parts. Most of all, they want to keep their clients happy so that they keep purchasing their car brand. They have a vested interest in making sure their clients have a good experience with that particular brand of car.
Yes, it costs a little more to get my car serviced at the dealership as opposed to Joe's garage down the street that works on every car that happens to drive in but I probably pay more in the long run due to inferior parts being used and for unnecessary repairs due to the issue being misdiagnosed by a third rate mechanic.
Let me see you get a computer component replaced at any place other than the dealer. Lot of stuff like filters and oil changes are available, like chargers and cases for phones, but not the proprietary stuff.