One good reason is because alcoholic beverages could be stored for long periods of time and be safe for drinking. Water can become contaminated over time if bacteria is allowed to grow while it’s being stored, so it has to be relatively fresh to drink. Other options like milk would spoil quickly. Alcohol generally didn’t have these issues, giving it some utility that outweighed its advantages.

In an age where other beverages are as easily accessible for people living in the modern world, it’s utility isn’t there any more and you are left with all the downsides.