Insurance

My insurers offered a hire car while mine was being repaired for 3 days. The car hire offered cover for damages at a rate of sum R40 per day which I was prepared to pay. But was then informed that I would have to pay upfront for 30 days which I refused. How can I pay for insurance of a vehicle that I would not be using. Is this a general industry practice? is so is it not illigal/overeaching? I have referred the matter to the insurer through my brokers about a week ago and am still awaiting an answer. I was so angry I did not take the vehicle offered which begs the point why have such a unreasonable clause in any insurance policy, my vehicle is ensured, was does the insurer not carry that responsibility for the hire car. Its the principal of the matter that I find strange.