When you buy a wine of an older vintage, it is an investment, and a wine cooler allows you to protect this investment. While you can store wine at room temperature, it is not ideal for preserving your wine.
Ideally, wine should be stored at a consistent temperature between 50° and 59° Fahrenheit and any temperature fluctuations can be extremely damaging to the delicate aging process of the wine. Wine coolers are designed to maintain a consistent temperature and will not fluctuate dramatically in temperature, which is particularly important for cellaring wine.