Believe me I understand that the job of repairing these high tech vehicles isnt all that easy. I am a field service tech for very expensive medical equipment, so I get it. Whats different for me, by the time I get to the second service visit for the same problem. Its devcon 5, I replace everything in order to just get the problem fixed no matter the cost. But in this case they had replaced everything, except the bags towards the end. There was simply not anything left to replace, yet they really resisted replacing the bags? The other components replaced previously, which did not fix the issue were a lot more money than the bags. Did I mention they had my truck on site for 5 weeks in total for just this issue.
Your relating of a "stealership" horror story is not new. The business model of a dealership is one of aggressive avarice, period.
Whatever the motivation that your dealer had for NOT replacing your bag, it, without ANY doubt, is one of ledger bottom line.
Sadly, our business model in this world has devolved into " Catch me if you can" and "One is evaluated by the month's bottom line".
On your subject, I have a Phillips Respironics that was a recall item due to the foam degrading and getting inhaled during sleep. I've since replaced it with a different brand unit, and stopped having respiratory issues. There is, and never was ANY excuse for this problem. And Phillips insults me with a 100 dollar repurchase offer for my old unit! Yup! Let's get rid of evidence! I kept mine.
Again, the mighty dollar rules and the fallout is a "potential" distant future quagmire.... so what if it negatively affects human life, eh?
I do not have ANY problem eventually getting to the root of these enigmatic car failures as far as the vehicles are concerned. The owners are the problem, likely unwittingly, because they typically are participating in "Hurry up!, I need to go and do YESTERDAY!" culture of our working world. Many go into mega-debt for a new car because they do not calculate the financial long game.
Ultimately, it took me downsizing to an artisanal business model instead of a production, cookie cutter grinder to be able to pursue my passion: Repairing those cars which have been to "X" shops and dealers, yet, after thousands of dollars, remain unrepaired. I'm semi-retired, and have the means and the patience to have fun tackling these types of challenges!
To quote my late mentor, the Rolls Royce Master, John Bamberg: Often the problems which are the most obscure or difficult to fix are "the 10 cent part and the thousand dollar headache"!