Fine until one suffers a serious injury or illness in a location where one has no coverage, requires medical evacuation, and goes into debt to pay for it all.

For the rest, if you think that your CC provides sufficient coverage, that is good for you. No need to spend more. If it does not, it's really down to your risk tolerance.

High quality insurance is not particularly on an annual basis. If you are suggesting that you've saved "thousands" I rather suspect that you are old and lucky or that you are of the misapprehension that purchasing from or through an air carrier on a per ticket basis is a good way to go.