California public schools tend to be relatively affordable for in-state students, so there is probably more satisfaction on that front than in some other states like Pennsylvania. The community colleges are usually a solid and inexpensive way to start a bachelor’s degree, with well documented course articulation to UCs and CSUs on http://www.assist.org . Additionally, many of the less selective CSUs do have majors like engineering majors that may be hard to find in some other states’ public schools.
But there are always some students who want to go out of state just to go away from home, who want to chase HYP-level prestige (and don’t get into Stanford), or who want some sort of academic or non-academic feature not found in the California public schools (or not found in the ones that they can get admitted to).
The UCs and CSUs do have a standardized weighted HS GPA calculation and a well defined set of HS course requirements, so that HS counselors should be familiar with them. They also need only FAFSA for financial aid, so the common divorced parent situation does not shut out students in that situation. Additionally, the application process does not generally require support from the high school, so that slowness or difficulty in getting counselor recommendations, teacher recommendations, and HS transcripts does not impede the application process (final HS transcript is required on matriculation, obviously).
The UCs and CSUs consider neither legacy nor race/ethnicity in admissions.