I think it's because of economic benefit. If you're alive, the government and society still make money off of you. People still consume, even if they don't work. Even if it's not you buying the resources or spending your money on them, they still need to be bought for you. Therefore, there's increased consumption. As long as you're alive, you will inevitably consume. A person alive is one more consumer. There are also potential ways to profit off of you. You're more valuable to society alive than dead. Only dead men pay no taxes.