Cheese and beer both have their sciences as does wine. No need to be defensive. They are all crafts which require a certain amount of experiance and practice to be perfected. That being said ...
Once the mashing is done and the wort is brewed it needs all needs to be fermented in something. The Mr beer keg is just another vessel like a bucket or carboy or even my V-vessel (which I love BTW) just sideways - sort of. It's brown color also restricts light and as I mentioned they fit nicely into a copy paper carton. They are very easy to clean, easy to pour leaving off trub in a carefully designed footpad and light weight. They work great for small batches and take up almost no room. Now if you were wanting to make large batch they would not be very useful but many people myself included often only want to make small batches or several different styles or experimental batches and they are perfect for that. I will say that I think their "Extracts" are ... less than desireable (or at least they were 10 years ago, they may have improved) but the little kegs are pretty neat. The bucket used to fermente the brew matters very little - it's the process of making wort and bottling or kegging that make the beer.