I'm convinced folks who complain about "unexpected recurring small bills on AWS" have never taken the five minutes it takes to learn to using the billing console.
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.
> five minutes it takes to learn to using the billing console.
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?
That's a good comparison. Have you ever cut yourself with a knife, any time in your life? I certainly have. I've also had a £150 AWS charge I had to pay.
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.
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.