So for public companies, custodians are essential, at least for now. While I think having Coinbase be the sole custodian is foolish, a custodial solution really is necessary.
Discussion
It's a matter of trust. I think there are many companies which could make a self custody protocol and implement it successfully.
But where you're dealing with hundreds of billions worth of Bitcoin, you can't leave that up to a single person or even a small group of people.
It needs active physical security, as well as professional cyber security and risk management. Having specialized professionals which handle this makes sense and there will aleasy be a market for it.