I think there's also a lot of idiot mechanics that blow smoke up people's a$$es and folks get a bad taste in their mouth and convince themselves they know better.
Good mechanics pay the price of that.
Here's a good example; I bought an engine from a NASIOC member last year, the seller provided all the papers from all of the dealer service on the engine, she ONLY had the dealer work on her car. About 16k miles before she decided to sell the engine to swap in a built JDM, she had new pistons put in at the dealer (she kept the engine bone stock until the warranty ran out). I installed the engine and it had a spun rod bearing :-(. The seller screwed me, she would provide a refund and wiped her hands of any responsibility saying I should take it up with the dealer.
That's not the point though.
I pulled the oil pan to check things out and here's what I found. Again, the car had ONLY been serviced by the Dealer over it's 60k life span so it was the DEALER's shop that dropped these puppies into the crankcase and decided it was cool leaving them in the pan...along with remnants from a broken wrist pin puller ST.