The Greeks and Romans made very strong and heavy wine which was always, with come ceremony (read the Iliad or the Odyssey), cut with water. I doubt anybody would die from dehydration on a diet of beer, even in a desert. But drink a fifth of 80 proof "Ol' Sunshine" neat while strolling through the Gobi and your point becomes valid.
Alcohol has been a part of human culture since before the invention of writing and the attempt to alter that by force of federal law was a disaster. The "War on Drugs" has been a quieter disaster, but in terms of the money channeled into the pockets of criminals, and on a vast international scale, it makes the grand experiment of the 18th Amendment (1920 to 1933) look puny in comparison.
In The Odyssey, the hero Odysseus had a supply of `dark and unmixed’ wine so strong it had to be `mingled with twenty parts water to one part wine’ to be safe for mortals to drink, and even then it `gave off rare scent and sweetness’ and still caused drunkeness.
When he and his crew were prisoners of the Cyclops and were being eaten one at a time, Odysseus plied the monster with undiluted wine into a drunken stupor, and then put out the wheel eye with a sharpened burning log (ouch).
Anyway, shedding the blood of the grape remains a noble endeavor. Look up the original meaning of the word “libation”.
What I am saying is that you will die of dehydration if you drink only beer or an equivalent wine.
Even in a long day of drinking beer, look at how your urine color starts reflecting the dehydration.
At your next overnight beer keg party, try to keep all the pass outs away from water or replacement fluids the next morning, and you will see the effects of true thirst on the dehydrated.