https://www.ecfr.gov/current/title-27/chapter-I/subchapter-A...
The only purpose is not to "jeopardize the revenue."
In that respect, regardless of the rate being levied, the result on behavior was intended to be very strict and immediate.
The intent is not to poison people, since the alcohol is not intended for consumption.
Morally and ethically such action results in a much worse outcome for society for many reasons. Unfortunately, that's not the view of many or those laws would not have been enacted. Even in our more enlightened times many still hold such punitive beliefs as witnessed by some posts here on HN. It seems to me opinion on whether or not alcoholic beverages ought to be permitted in society has been around so long and yet still remains so divided that the chasm will likely never close.
Fortunately, where I live (Australia) the toxic denaturants in ethanol (methanol (~15℅) and pyridine (~3%)) were removed quite some decades ago and replaced with a nontoxic denaturant—the bitterant denatonium.
We nevertheless still have a lingering reminder of the past: the once non-potable ethanol was called "Methylated Spirits" and its replacement still is! Nowadays, the methanol and pyridine are gone and what's always been colloquially nicknamed "Metho" is still labeled "Methylated Spirits" but now only consists of 95% ethanol and 5% water—the trace amount of denatonium denaturant isn't even mentioned on the label but it's definitely there.
An interesting observation: the old toxic methylated ethanol was emblazoned with the word "POISON" whereas our new Metho sans MeOH is only labeled "CAUTION".
BTW, above I mentioned the chasm never closing, whilst writing this my earlier post has oscillated wildly around a net 0, I now have the same number of votes that I started with before posting. Seems opinions are even more divided on this subject than I'd ever imagined (damn shame HN only tallies totals and not both up and down votes).
Note that we are talking about industrial alcohol, which was not made for human consumption but could be distilled to make it palatable (before the toxic additives were added).
Depends in which country you reside. Where I am the denaturants methanol and pyridine were removed decades ago and replaced with the nontoxic bitterant denatonium.