You do realize that in bitcoin world you can always have your own wallet right?
Imagine running a large pension fund or institutional firm like that. Your expertise is in market hedging, not network and key security. With billions of dollars on the line, do you really think it's wise to gamble on self-storage? You're going to be a big target for hackers.
That's going to be the mindset of most (if not all) institutional traders. I don't like it but I also don't see any way around it.