Why is that the case? Does a mixer try to follow the entire way of Bitcoin funds, and if the "path" is intransparent,
mixing is not performed?
There are 21 million bitcoins ever exist and those coins can be circulated on the market. Very old bitcoins from Satoshi Nakamoto era can still be used today and coins can be used as inputs, outputs for anonymity sets in mixing process. After that, outputs will be tainted by chain analysis and centralized exchanges that are strongly against mixed coins. Because centralized exchanges have to obey laws, AML, and what happened with Binance, Kucoin recent months are big red flags for centralized exchanges to be stricter against their customer deposits.
You can understand more about tainted coins with this video.
Bitcoin Q&A: Blacklists, Taint, and Wallet FingerprintingIf you have questions, you can ask him on X, and ask him to update more information about this issue with recent serious changes in regulations in the USA. and globally.