That sort of thing makes more sense than you'd think - if people earn money at a brewery, spend money on beer, and handle decisions about large amounts of beer on a daily basis then it encourages them to perhaps find an excuse to 'spoil' beer then take it home.

If everyone gets a ton of free beer anyway, then most people won't be tempted to nick some booze.

Making it tax-free makes some sense, because nicking the booze is also tax-free.

based on the breweries in the USA i've visited, it's very common here, too. i somehow doubt it's because all the employees would otherwise be beer thieving criminals, though.