Many people choose to pay their auto insurance premium in monthly installments rather than paying for it in full. The reason people do this varies from person to person, but usually it involves money. Because people sometimes do not have the lump sum of cash to pay upfront, they opt to set their policy of almost the payments. This basically is just financing your insurance policy, and because it is a loan you'll likely pay interest on it.
Another reason people choose to pay their car insurance monthly rather than semiannually are annually is that they want to hold on to their cash. The reason for this is obvious, with the decline of the Western economy people are nervous that they may lose their job. If they did lose their job, I'm sure they would rather have a little cushion in the bank than not.
Really, if you do not have the money to pay for your auto insurance policy up front there's nothing wrong with making monthly payments you should just be aware of the fact that you will be paying a high interest rate.
But unfortunately this is not the only downside, there are also many others. Among these are the fact that you would typically pay far more in the long run for your policy if you pay for in this way. This is because you will not receive the discounts that other members receive when they pay their full balance in advance. Some companies offer discounts that make it cheaper to pay three months at a time within two months. This is meant to discourage members from stretching their payments out into monthly installments.