It's called responsibility and balance. Yes, I could throw all of my money in a high interest account and have absolutely nothing available to me and have to rely on borrowing like you suggest, or I can keep a chunk of money in accessible accounts in case of these emergencies you mention, and put the rest in higher yield investments. You should never tie up all of your money at once, that's common sense of financials. You guys all seem to have an entirely different mindset of borrowing money being the cool thing to do. That's the issue our country has today, people would RATHER borrow money than be responsible ahead of time. Like Brandon just said, it's gaming the system. In your opinions it's better to game the system for every last bit of interest rather than have the personal responsibility to know you can cover what you need to pay, when you need to pay it by yourself without having to borrow money.
Like I said, having a credit card just in case is not a bad thing at all. It's a valuable tool that when used right is great to have. But I wouldn't start relying on it to be my emergency fund at all. I consider that irresponsible. And you most certainly don't need to have one, nor are you handling your money wrong to not have one. Credit cards are the easy way to have backup money without actually having backup money. So what if I missed out on a couple hundred dollars in interest over time. I didn't LOSE any money though, and I have the personal satisfaction to know I can cover my own ass without having to get someone else to cover me.