For most people it's that you are only familiar with what you grew up with. I was lucky enough(I guess) to grow up in a country where calling for an ambulance was a no-brainer, never ever seen a single medical bill for anything, and also where I've personally called the police about problems I've witnessed - all interactions with officers were polite and I wouldn't hesitate to call the police again. That's why it's so hard do understand for me that there are places like the US where it's not the case, and calling for an ambulance can put you in massive debt - it's just upside down when I think about it.
Not only can calling an ambulance put you in massive debt, which it does (not merely "can") in America, but interacting with the police is almost unanimously unpleasant in my personal experience. (Report a handgun discarded on the side of the road, get harassed because you don't carry photo ID every time you leave the house on foot, etc.)
