I suspect it's a labor thing as much as anything else. My father lived out his life at home, so I didn't have to deal with assisted living. However, the IRS is crystal clear that domestic employees are in fact employees subject to all the things like overtime and UI. California has even more generous overtime rules, but even just the base pay gets expensive. $20 * 24 * 7 = $3,360 in base pay per week. Using an agency simplifies things but is usually a bit more expensive.

Assisted living, in general, is phenomenally expensive. It sounds like the mother lived in Sacramento, but they're renting out her house, so I'm sure that's a welcome revenue stream.