Cash is not completely anonymous, but hard enough and not enough parties track it. Bills are serialized and you could take photos of coins and likely identify them based on scratch patterns.

Still, whole thing is saved by not enough people actually tracking it to that level.

And on other side, BTC tracks every single transaction ever. Which is also detriment, that is we keep everything stored forever in lot of places... Which kind seems massive waste.

Point taken about anonymity. However, its design (that of cash) is theoretically anonymous, it is reality which gets in the way. BTC, on the other hand, is "just" a huge ledger of transactions with giver and receiver perfectly "identified" (in a unique way, albeit just pseudonymous) and preserved forever.

Also, as you point out, BTC is a massive waste of resources and storage space.

> giver and receiver perfectly "identified" (in a unique way, albeit just pseudonymous)

Not perfectly. A lot of heuristics are needed to link a unique owner to multiple transactions. With bitcoin, it's recommended to use a new address for every transaction so, for example, in a basic transaction, it's not so easy to identify which output is the recipient and which is the change.

And there's Monero that tries to hide these links a lot more.

Which is why higher layers like the Lightning Network, Rootstock, Liquid offer to not store everything on chain and offer speed/features Bitcoin natively can't while resting on the higher security model of their base layer.

There was a great article in a German magazine some month ago, they are listing very detailled how cash tracking works and who is involved and which process step: https://netzpolitik.org/2025/reise-eines-zwannis-diese-gerae...

Its really interesting, feel free to use your favorite LLM to translate it :)