A few reasons: Houses are perceived as good stores of values as prices in the Bay Area generally trend upwards. There is more trust in a house vs the stock market (or the investor has a diversified position and real estate is part of that diversification). Cash sitting in a bank is getting devalued with inflation. Real estate can also generate rent if you don't reside there.

Another angle, the house may be owned in another person's name, then the illiquidity is an advantage. The other person who you trust, may still be tempted to use tiny bits of large chunk of cash if its sitting in a bank account. Meanwhile selling a house is a pretty big deal.

The reason for not keeping the house in your name are possibly related to avoid the local government's oversight into your assets, etc.