A for profit insurance company's business model is precisely the same as a casino. Every policy they write -- like every play on a slot machine -- is a positive expectancy bet for them and a negative expectancy bet for you. They've done all the math and they understand the risk/reward on all of their policies a LOT better than their customers who just 'know' they 'need insurance'. Unlike the casino, though, insurance companies have an additional layer of nastiness where they can and will welsh on payments when they lose the bet, as in this article. Some of that can be legal, say where they just understand their policies better than their customers (the customer wasn't as covered as they thought they were). And some of it can be downright nasty, where they will just refuse to pay or underpay and see if the customer has the resources to take them court.

On average self insurance is a much better investment than an insurance policy. However, that's with the caveat that you have to have the money set aside (preferably in a low risk investment) to cover your worst case risk, and you have to be realistic about what that risk is.