A better reason they should struggle is because they often use aftermarket parts on the low end of the quality spectrum and charge as much, or more, than a dealership. My dealer changes the oil with synthetic, vacuums and dusts the mats, floor, seats, and dash, gives a complete check over sheet listing brake thickness and tire tread depth, and rotates the tires for $65.99 or, $55.99 if you have a coupon. That's like an afternoon of work if I do it myself and I'd save about $30. Plus they caught a leaky water pump a few months ago on the wife's car. And it wasn't a scam. Because I said, "I haven't noticed significant coolant loss, only a couple cups every few thousand, so I'll wait on the repair." And it got worse and worse and worse until, magically, it pretty much vomited coolant during even short trips from the timing belt cover area. New water pump and doesn't do it any more!
Plus after waiting in line it's like a 30 minute+ process. I can eat cookies, bananas, and granola bars at the dealer and have soda, water, or coffee while watching something on TV that some other customer thinks if interesting, like CSPAN.
