Insurance is like gambling, don't overdo it
My take as a finance person but not an insurance person:<p>- Some events are low probability but high cost. You're unlikely to crash your car, but if you do, it might cost you a heck of a lot to fix. Nearly everyone is in this situation, so it makes sense for everyone to pay a little at a time and give that pot to whoever ends up crashing.<p>- The insurance pool cares about the average outcome, ie average cost. They need to collect more than this. The insurance buyer cares about the extreme case, where they end up crashing. So in there we have space for a trade. Yes they care about the extremes too of course, since they wouldn't want a bunch of payouts at the same time, but that's something actuaries have thought extensively about.<p>- You want people in the pool to be similar risks. If they aren't and they know they aren't the low risk people will decide they don't need to insure, leaving everyone else with a higher average cost. Also, the high risk people will see a good deal and join. Adverse selection.<p>- If the thing you're insuring isn't a catastrophic cost, you're less likely to want to pay over the odds. Maybe your £200 phone doesn't need a £30 annual insurance, because you have lots of money to buy a new phone. If you're really rich maybe that car crash scenario doesn't matter for you either (but of course there are laws about insurance).<p>- The insurance company holds a free float. All the premiums are coming in, but only pay out now and again. That gives some room for investing the free float.