Privacy was one of the core goals of cypherpunks that predated and led up to the creation of Bitcoin

As for advantages of using Monero over cash...

-Can't use cash to transact instantly with anyone on the planet.

-Can't carry arbitrarily large amounts.

-More vulnerable to confiscation and theft.

-More difficult to verify authenticity on-the-fly.

-Issuance is centralized, unpredictable, and doesn't require PoW.

-Not as easily divisible (Need to carry specific denominations and change)

-Can't trustlessly exchange for crypto (no atomic swaps)

-Can't have multiple people with simultaneous ownership and control over the same cash (multisig)

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