Your insurance company example is totally unrelated.
A well-run insurance company spreads risk among all of its customers. There are NON-PROFIT insurance companies that do an excellent job of spreading that risk around (Kaiser Permanente spends 95% of its insurance dues actually paying for medical care, for example). When you buy insurance you're not EXPECTING to have a problem, but you want to be protected if you do. When someone DOES have a problem, the insurance company hasn't "screwed up" -- the entire point of insurance is to cover unexpected problems.
The only time that the insurance company could be said to have screwed up is if they're losing money overall. And in that case they'll eventually go bankrupt.
>why do people choose to pay them?
Ignorance? Given how many times I've seen advice to never (or at least only rarely) place a market order, I have no idea why anyone does.
Or possibly it's just the "greater fool" theory: They will sell to the HFT if and when they think they know better than you do.
You're claiming that the HFTs are providing insurance to the people who are buying or selling? I find that to be a stretch, since the entire point is that you look for sure bets and attempt to only sell this "insurance" to people who (in your opinion) don't need it.
And frankly most people trading in the stock markets don't know they're even "buying" this insurance. If they did, then yes, I could buy your argument. But they don't. And the ability to choose makes all the difference in this case.
I'd like to hear from someone trading stocks for a mutual fund, and whether they would "choose" to pay an HFT.
The reason that we don't have market makers standing around in pits any more -- that computers can do the trades directly -- also implies to me that we don't need those intermediaries at all. There's a lot of economic leeching that goes on in Wall Street, and I suspect that much of it is obsolete. HFTs are merely another symptom of the same problem.