why should they do this just for Bitcoin ATMs but not enforce it in any other business / store / you name it?
I don't know. I just noticed that banknotes are processed very slowly by some Bitcoin ATMs, that's a lot faster in a typical bank ATM, where you can put a lot of cash, and everything is counted very quickly, like 10 banknotes per second. I wonder if that delay is "by design", if they check them more carefully, or are they trying to trace them by reading serial numbers? I don't know, I can only guess, but 10 times slower counting is suspicious. The currency is the same, all banknotes has the same shape, so I wonder why banks can count them faster. I wonder if banks have better hardware, or if Bitcoin ATMs use more advanced tracking, just to comply with some local law of preventing money laundry.
Oh I highly doubt that Bitcoin ATMs check for serial numbers on bank notes. Pretty sure that if they're slower, it's just since they use different hardware (probably lower quality). But I'm sure there are different brands, different models and what I saw so far, was just as fast as a normal bank ATM.
If they were to reject certain serial numbers, we would also definitely have heard about it on the internet.
See monero. It's, supposedly, more private than bitcoin. What has happened? Most CEX's have blacklisted it, less and less merchants dare to accept it, people beyond the crypto space are constantly brainwashed etc. Is the problem in the code?
The problem, as you alluded to, is that we can evade all kinds of laws with software and technology, but in the end we live in a society that has rules, like not to launder money. Sure, technology can be written and improved to make it more easy to launder money, but it doesn't make it legal.
So if you own billions in XMR and one day you suddenly want to buy a private jet with it, it will be
very very hard to do. And there's no technological solution to this issue to be fully honest.