Decentralization is peddled almost to the point of absurdity.
Most individuals don't know how to secure their crypto funds well, or are unwilling to invest the time to do so.
So they may use insecure brain wallets, or insecurely store private keys.
Why exactly would outsourcing crypto-storage to an entity be somehow more insecure than insecurely storing it yourself?
Plus the stake are higher for third parties.
In fact, to achieve some balance on the matter, it'd be worth considering the amount of priv. key hacks that individuals suffer in a specific period of time vs. entities that manage the secure storage of groups of private keys.