Because this didn't exist in the 20's, the government started adding poison to alcohol not intended for drinking -- because people were drinking it, predictably, and bootleggers were reselling it to be consumed -- and killed thousands of people in the process.
Denatured alcohol still does nasty things to people who are ignorant and/or desperate enough to try not-for-consumption alcohol... fortunately it's not so deadly nowadays (I think?).
Obviously the people drinking alcohol in liquids not meant for consumption aren't in normal rational states of mind; but yes, they're doing something really stupid. But suppose when you're "denaturing" the alcohol in your product, you have the choice to use a substance that will make it taste very bad and cause vomiting; or a substance that will make people die, or at least go blind. Which should you choose?
Next, suppose that the alcohol was stolen and resold by a bootlegger and thus has no warning (beyond the government's warnings that buying illegal alcohol is dangerous, which had already been going on for some time).
Because this didn't exist in the 20's, the government started adding poison to alcohol not intended for drinking -- because people were drinking it, predictably, and bootleggers were reselling it to be consumed -- and killed thousands of people in the process.
http://www.slate.com/articles/health_and_science/medical_exa...
Denatured alcohol still does nasty things to people who are ignorant and/or desperate enough to try not-for-consumption alcohol... fortunately it's not so deadly nowadays (I think?).