I do understand your point, but I think there's a difference between evidence and your method of detection.
Sure, and our process consists of much more than just detection of an irregularity. After detecting something weird or suspicious, we investigate, discuss where necessary, and arrive at a decision. This is not a random process. And it is important to keep in mind that breaking the rules does not automatically result in a ban. Banning is just one extreme of the scale.
Also I don't think everyone caught of cheating intends to cheat again or even know they were cheating the first time.
The "I didn't know" defense is typically not accepted in real life. It is not something we can accept here either. Everyone is supposed to read the rules, they are available in native language for almost all users. That is pretty much the best we can do to give everyone access to the rules. Even with the expectation that every user knows the rules, we always consider the severity of the case. If the crime is not that bad, if the user and their behaviour seems more ignorant than malevolent, a warning is typically issued. Here, the expectation is very much that once caught cheating, the user will understand it is better to continue playing nice.
Also there could be coincidences that could be misinterpreted as cheating.
Sure, anything can happen. It is however highly unlikely that such a case results in a ban. The process is not random. You would be surprised how much work goes into the investigation of some cases.