How is a deposit not practical? Unless they require it in cash that has to then at the end be picked up at the pickup point (which would be crazy)? A rental company is taking a huge risk by renting cars to any random person with a driving license. It's the same reason they don't typically rent to people below 25 (or without a higher deposit).
It's really only unpractical if you don't have enough money on your account to afford the deposit, but then why are you renting cars? Otherwise you just pay a bit more the first time and then get that money deposited back on your account when you return the car. There's basically no difference in the end other than a bigger number the first time, and if you wreck the car or something, you will lose the deposit through your credit card too.