Nowadays it is standard practice for most car hire agencies companies to require a credit card at the time of collecting the vehicle or booking online and many car rental companies will not accept debit cards or cash payments at the moment you sign the rental agreement. The most important reason is that the car hire company cannot process advanced charge approvals against debit cards, another reason is that they try to avoid handling cash at the counter. In essence your credit card is held as a security deposit against possible losses or damages to the rental vehicle.
Original text: Car Hire Without Credit Card