> Why can't non-institutional actors achieve the same level of privacy?

Non-institutional actors are transacting over an immutable public ledger. Institutional actors are transacting via backchannels. In other words: the cryptocurrency transaction space is "schizophrenic": the traffic that supports high valuations is not settled on the chain itself, but via gentlemen's agreements. Non-institutional actors could do the same thing (and get the same privacy), but then it's just normal money laundering instead of "decentralized finance."