Re: Why do most wines contain no more than 12% to 14% alcohol?

Wines are fermented via yeast.  The yeast metabolize the sugar of the 
grapes to ethanol.  As the ethanol concentration increases, (sugar 
decreases) the yeast activity decreases.  Eventually, (12-16%) the alcohol 
concentration becomes so great that the yeast can no longer metabolize.

Wine makers can control the alcohol content of the wine by the sugar 
concentration of the grape slurry, temperature of fermentation etc.

ALcoholic beveages with ethanol concentrations above about 16% are 
normally distilled or mixed with distilled spirts.