Odaily News: Vitalik Buterin stated during the Bankless Podcast that he did not stake all of his Ethereum, but only a "relatively small portion" because securing the stake on the network requires multiple signatures, which is still a complex process.

Buterin explained that if you stake your ETH, the key to access it must be publicly exposed in some online system. For security purposes, it must be a multi-signature setup, and setting up a multi-signature for staking is still quite challenging. It has become complex in many aspects. (Cryptoslate)