Mountain View has about 6,000 people per square mile. Cupertino has about 5,000 people per square mile. Palo Alto has about 2,500 people per square mile. Etc.

By contrast, a suburb full of real housing can be far denser. For example, Somerville, MA, a suburb of Boston, has about 19,000 people per square mile. It’s entirely unnecessary to fill the whole of the Bay Area with 30+ floor high rises in order to increase density by a factor of 2 or more; all we need is to re-zone a fraction of the land to allow 3–6 story low rise apartment buildings in mixed-use neighborhoods instead of only allowing single family detached houses on large lots and scattered strip malls and outrageous numbers of parking spaces everywhere.

Kowloon has a density of more than 100,000 people per square mile. The Bay Area does not need anything near the density of Hong Kong to meet its housing needs.

Of course, Somerville has little parkland, and few commercial buildings, not even much retail, and little office space.

I'd much rather see balanced communities with parks, retail/entertainment and office space so many residents don't have to travel outside of their community for every day needs.