I believe the argument is that it makes it easier for institutions like fund managers and businesses because they don't need to be concerned with custodianship.
That may have made sense 8 years ago, but the problem has long since been solved. Coinbase can act as a custodian for your Bitcoin. Fidelity has its own service for it, as does every other fund/brokerage/bank of its scale. You can buy it as part of your 401k.