Because, two of those programs could be considered scams. They don't actually DO anything except generate a pretty report. I won't say which two are the scams, I'll just say the following.
1: A few months back there was a concerted effort to astroturf glary utilities on this forum, probably others as well
2: Registry programs tend to cause more problems than they solve
3: No registry program I have ever seen actually gives some kind of objective selection criteria, which I find to be quite interesting in a disturbing sort of way... Both in that you have no idea what's going on, and that I seem to be about the only person on the planet who stops to question that
4: Avast is the only product that has undergone some kind of objective testing by a neutral third party
I don't care if you believe it was the intervention of a divine being or just a long string of coincidences. The point is, humans have brains which are capable of analytical thought. So be it because of some divine being's benevolence or because there was some evolutionary advantage, it seems rather folly to not be using that particular part of your brain. Either you're insulting said divine being, effectively throwing its gift to you back in its face, not to mention being supremely presumptuous to think that you know better than it what you need... Or you're simply not making use of every evolutionary tool you have to succeed... It brings you right back to it being folly not to use it.
You don't need to be an expert on everything to be able to think things through logically and figure out when someone's trying to scam you. For example, does it REALLY take that much effort to figure out that some random person on the Internet, whom you've never before met in any way, sends YOU an email saying that they suddenly inherited all this money and need YOU to help them hide it from some government agency? You'd think it'd be a no brainer, yet thousands of people fall for this rather primitive scam every day. Now if you want to join them on the list of people natural selection needs to deal with, I commend your willingness to remove yourself from the gene pool for the betterment of the species. OTHERWISE, start giving the analytical parts of your brain a workout from time to time. Then these things will become self-evident.
And just to help prove the point. If you are upset by anything I said in this post, it's because on some level you know I'm right.
Why do different softwares find problems when run back to back? I am trying Glary Utilities and WinUtilities along with Avast virusware. Each scan from each one finds the same stuff, even after I repair. Why? And how do I know which one is best and which to purchase?