One of the biggest sources of "lost" tax revenue is the "underground economy". There are millions of people working throughout California on an under-the-table basis as privately-hired domestic workers, caregivers, and more.

The problem is, to enforce the tax laws against the homeowners who engage in this employment activity but who do not withhold or pay taxes, the government would have to audit all of them. Not very likely, especially not the frail and elderly seniors who receive much of the caregiving services.