20% of all bitcoins have been irretrievably lost [0] and 7% have been stolen [1]. If I was the global rich, I'd rather hide gold bars in my mattress rather than put it in Bitcoin if my goal was just security.
[0] http://fortune.com/2017/11/25/lost-bitcoins/ [1] http://www.businessinsider.com/how-many-bitcoins-have-been-s...
Edit: for large institutional investors in a trust fund
This is only the case for this particular trust fund. You can secure your coins for free on your own.
edit: downvoted for stating a fact? really?
Peoples money gets stolen all the time.
Proper techniques to store bitcoin (local keys on a secure machine or a hardware wallet) make bitcoin mathematically impossible to steal. "Stolen" bitcoin is synonymous with "insecure" bitcoin. Properly securing bitcoin would be significantly cheaper than storing gold bars in a mattress.
Edit: Just in case it's not clear, my point is not that specifically bitcoin is more vulnerable to violence/coercion than other forms of value storage (although I'm pretty sure it is, as there are fewer safeguards/redress mechanisms). My point is that the regardless of the security of the mathematical element, cryptocurrency also has the real-world to contend with, which contains bugs, hardware failure, extortion, phishing, memory loss, theft, etc.
So many coins have been lost because people were careless or uninformed, not because the system is fundamentally broken.
Edit: You're free to downvote, but if you can't make a reasonable argument against me it just shows the emotional response you are leaning on. I would be happy to post a wallet address with $10,000 in bitcoin on there, if I am wrong about what I said, surely you'd be able to take the money from me?
I agree with you that downvoting without offering counter-arguments is a sign of emotional rather than intellectual responses... but so is using straw man arguments like the one you put up.