Sixish months ago there was a fire in our condo building. Fire damage was limited to one or two units, but a lot of the building suffered water damage and was declared uninhabitable by the city until cleaned up. Our unit and many others were completely undamaged but we had to move out on one day's notice anyway. We found a small place with exorbitant rent and dealt with moving expenses, mail forwarding, etc, meanwhile mortgage still needs to be paid. Without insurance what would we do? Get our money back from the resident responsible? It's been six months and the condo insurance (the condo insures the common property, individuals have to insure their own units and contents) hasn't even started court proceedings as far as I know and they employ lawyers full time to handle these things. So what hope would you have? Again, meanwhile you still have to fork out rent on top of mortgage. Besides, in this case the responsible party has no liability insurance (they would have been covered if they had hired a certified plumber...) so there's no money anyway. Lose lose, they get to go bankrupt and you get nothing.
Some people in the building had problems getting their insurance to pay up - that's what you'll hear stories about. Again it pays to read the fine print. Luckily our insurance covered everything and sent out cheques same day.
Of course, the renters in the building just took their stuff and moved out. They had a hassle but not a financial loss.
Warren Buffet talks about insurance a lot, which is a major (his biggest?) business for him. According to him, the major profit in insurance is investing the pooled payments. They pay out more in claims than they take in payments from customers. It's not a scam, it's a business. Whether you need the service or not is up to cost-benefit analysis. As others have pointed out, the rule of thumb is to insure against catastrophic losses, budget for normal costs.
PS obviously I'm not an expert. I've just had to do some reading up on the subject recently.
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