Insurance companies are just like casinos in that the math always favours them if you look at a sufficiently large sample size. Even so, some things are still worth insuring. e.g. Your house. Most people do not have enough assets saved up to replace their house should it burn down. Even though your house will likely not burn down, protecting yourself against the loss of something you can't easily afford to replace is worth spending money on.
Does it make sense to insure things you can replace though? Consider the "Instant product replacement" plans that stores constantly try to sell you. If your monitor dies you can easily absorb the cost of buying a new one. If, instead of buying IPR's on everything, you set aside a similar amount of money, you'll likely soon come out far ahead. Even if you don't, you'll still be able to afford it. Buying IPR's means, on average, you lose money. Not buying IPR's means, on average, you'll save money. The choice is easy.
Insure the big, vital things you can't afford to replace. Treat insuring small things as gambling without the fun.