It's like asking why the knife you're using keeps cutting you when you put your finger on the sharp end. Learn to use your tools, and they won't surprise you. Learn to track your costs, and you won't have unexplainable recurring bills.
Most cloud providers don't have this billing problem and so the analogy breaks. Its more like, why does this knife keep shooting me in the foot?
I spent hour or two trying to find anything running and didn't find a damn thing. Yet Amazon decided to charge me a buck or two every month for "storage" so I just canceled whole account. I mean, if I can't find what I am paying for when not using it, how am I supposed to understand the bill when I actually have a dozen of instances?
In both cases I learnt my lesson. I'm careful not to put my fingers where a knife can cut it, and to not put my bank details where AWS can charge them.
100 of them have provided an opinion and 99 of the opinions are that it is. Everyone in the room is bleeding.
I think it's fair to say that there's an issue with the tool, Stockholm syndrome not withstanding.
You can even enable scans for unused respurces that generate costs..