It certainly makes it easy for the dealer to pass the buck- when you're having an issue with a particular unit, their "guy" for that brand is from another dealer, so now 1)- you can approve that another tech who's not as saavy try to fix a problem ( & pay for elongated time 'cause he's spinning his wheels or 2) wait for their "guy" & pay for elongated travel time & hope he doesn't need parts ( he can't go to the local dealer for parts- he has to go to his home dealership). Either way it's a lose- lose situation for the customer.

When the salesman knocks on the door- he sells the multiple brand/multiple dealership as a plus- it all goes downhill once you actually use their services