Is Insurance really useful?

Insurance, as what I understand, it can provide you a certain level of protection depending on the insurance package you have purchased. Well, to many of the people who does not have financial stability, it can really provide you some basic protection in terms of money. But to me, I would rather depend on myself coz sometimes if you put too many hope on other people, you may be dissapointed. I understand the fact that a company can exist is because they make profits..Do you think an insurance company really puts their clients in their 1st priority? Well, it may or it may not.. Why not you do a basic experiment by yourself by claiming from your insurance company whenever you are sick and let's see does an insurance company can approve your claims all the time? If the answer is yes, then congratulations, you have buy insurance from a good insurance company; if not, think twice before you buy an insurance next time....