I think the issue of insurance depends on your situation and whether you are in a position to find lots of money very quickly if things go wrong. I am cross with myself for not checking things out more thoroughly as I thought a staffy and a mix breed are going to be healthy anyway so probably won't need the insurance but good for emergency back up, I should have asked vets for bit of advice as turns out my vets won't do direct claims with them as they are notorious for taking an eternity to pay. I had to find 2 grand a few days before Christmas and have spent a lot more since, even if I'd known about cheap European treatment Lu was far too poorly to travel. I was very lucky my mum lent me the money and I finally got it back from insurance about 6 weeks ago. Even with insurance there are many people I am sure, who would have not been able to afford treatment costs up front so then what would happen. Lu is stuck with those insurers now but I changed Rosa straight away so I know if she ever needs emergency treatment all I need to pay is excess and vets deal directly with insurers to settle the balance. I would say if someone isn't in a position to find alot of money very quickly then insurance has to be preferable to alternatives but choosing a company that vets are willing to deal with directly would always be my priority in future. I cannot fault our vets for Lu's treatment, I am very sure that Lu's welfare was only consideration of staff and they discussed every single test he had with me and did nothing without full explanation that I was able to check independently (admittedly afterwards as at the time I told them to do whatever they had to and not worry about cost as I was so distressed) but everything they did completely checks out and they have no issue with raw diet now his immune system is no longer suppressed, I don't know about high turnover of staff but if Lu's vet leaves I will probably follow her if possible as he adores her and he doesn't like anybody! Rosa would be happy to see someone new every time as would be exciting to make another new friend!
And even the hardiest breeds can have terrible accidents, a good friend of mine who works for a large national rescue was walking her dog responsibly on a lead and she was badly attacked by an off lead dog with no owner in sight. (Dog was attacked, not friend) and this could happen to anyone and again, a dog fighting for life like my friends couldn't be travelling abroad or shopping around and insurance for those of us who don't have $$$ is only way we can guarantee instantaneous treatment. Even though Lu's insurers were rubbish I would still rather be ripped off twice by them and vets rather than lose my companions unnecessarily
By the way, this doesn't mean I don't fully agree with op's reasoning that the very existence of insurance pushes vets costs up but while UK vets fees remain significantly higher than Europe if we aren't in a position to pay for them then for some of us insurance is our only option
If it wasn't for my dogs, my house would be clean, my purse would be full but my heart would be empty