Why do insurance companies charge a high interest rate when paying monthly?

My house insurance is due for renewal in March. I usually pay monthly because it helps the cash flow, however I've recently (re)discovered that my insurance company (who will rename nameless... I think they're mostly the same), charge me around 10% APR for the privilege of paying monthly.

As you may have gathered by the content of this website, I don't like paying interest. Sometimes however, it's understandable. Most things you buy on credit are real, physical items which you get all the use out of right away, but insurance is different isn't it? When I pay for insurance yearly, I still don't get insured for December until December, so why should I pay for it in March, and more to the point, if I pay for it monthly, what gives the insurance company the right to charge me interest on it? By rights, I should be able to pay monthly at no extra cost, and if I decide to pay yearly in advance, then they should be paying me interest.

The nice lady on the phone agreed with me, but of course "Computer said no", so come March I'm going to attempt to pay for it all in one go, simply to avoid the interest.

Just another example on how these companies make money from the little people.

<sigh>