If prohibition doesn't work, why does it still exist?

Fact is we will never be able to stop people from using any drug, just like we couldn't stop people from drinking alcohol back in the 1920's and early 30's. So why should the tax payers have to pay the price of prohibition when there is a logical solution to this problem...I mean the reason why criminals are involved with drugs is because of the very fact that they are illegal. Instead of building bigger prisons to house these non violent offenders on the tax payer dollar, we could take a more progressive approach and save Americans literally billions of dollars. Even Abraham Lincoln said he would not be in favor of supporting prohibition "Prohibition will work great injury to the cause of temperance. It is a species of intemperance within itself, for it goes beyond the bounds of reason in that it attempts to control a man's appetite by legislation, and makes a crime out of things that are not crimes. A Prohibition law strikes a blow at the very principles upon which our government was founded." This man was one of the greatest presidents in our history, and if you disagree with this quote you are very misguided.