Pot sills are primarily used for distilling low alcohol by volume (ABV) with a high degree of flavor. Your average pot still will yield alcohol in the range of 40% - 60% ABV and will carry over many flavors from your fermented materials. This is important for anyone making flavored spirits such as whiskey, rums, etc.
Higher proof spirits can be achieved by doing additional spirit runs or using additional still components like a thumper, just keep in mind with each additional run you will yield less alcohol and you will lose more and more flavor as you increase the ABV. If high proof spirits are what you are after you should consider using a reflux still instead.