Not necessarily. Oak barrels are a staple of traditional winemaking, and most red wines (and many whites) feature oak barrels in their process to some degree. However, hand-coopered oak barrels are quite expensive, and they must be kept meticulously clean or they'll spoil. Many home winemakers avoid these hassles by using oak chips. These are produced from the same wood as barrels (from forests in America, Hungary or France), but they are very cheap and easy to use. They simply need to be added to the fermentor until their flavor is sufficiently absorbed. Eventually, most advanced winemakers invest in barrels, either alone or as part of a winemaking group. Why? Well, the effects of oak aging are more complicated than just the wood flavor imparted. Since oak barrels can "breath," a slow, complex process of evaporation and oxidation occurs during barrel aging. This lends much more complexity and roundness to the wine than can be achieved by aging in glass or stainless steel. Commercial wineries that age their wines for 2 to 3 years in old oak barrels are relying on this process, rather than on the flavoring potential of the wood.