There are various reasons a beer may be stronger than others. In our modern time, the catalyst making a stronger beer has often been the desire to make the strongest beer. That was the one and only goal. This led to making beers that went beyond the formerly strongest beer called Samichlaus (which means Santa Claus…merry Christmas indeed). Samichlaus hovered around 14%. Samuel Adams (i.e., the Boston Beer Company) made a beer called Sam Adams Triple Bock, which was the first in the extreme beer category. The beer weighed in at 17.5% alcohol. Even more amazingly, Sam Adams makes a beer called Utopias which is upward of 25-26% alcohol. All the qualities and merits of these beers cannot be fleshed out here. However, let it be said that these beers have their own merits and great (albeit robust) qualities. Before the “extreme beers” there were just really strong beers.
Why were some beers made stronger than others? It seems that, for the most part, practical considerations were the real driving forces behind stronger beers. Whereas we in our modern life often drink to escape misery, sadness, or reality (a.k.a., emotional pain). I realize that this is not all of us, but that is the nature of a generalization. People have often drunk stronger beers to escape the reality of physical pain. A much larger percentage of people in the past were physical laborers. This might have been dictated by ancient agrarian life, indentured servant-hood, or slavery. It is also my opinion that people in the past were probably less introspective than are we. Either way, people generally had harder lifestyles. Without the the comfort of modern medicine, these people turned to alcohol as an analgesic. Of course, the stronger the beer the greater and sooner the relief.
The second practical concern that people seemed to have was the necessity of empire or trade. Some of our familiar styles such as I.P.A.s came from this necessity. In order to be able to ship beers long distances, they had to be made stronger in either hops or alcohol or both. Stronger alcohol and hops gave longer life and more resistance to bacterial problems. Once again we can see that in former times, beers were stronger out of necessity. This is not the case with modern beers.
What I find interesting is that higher alcohol beers have come into their own as beers to be enjoyed. I think its worth pondering.