Employment in California is “at will”, meaning that absent extenuating circumstances (such as a written contract) either the employee or the employer can terminate the relationship at any time, without cause. So, it’s not hard to terminate someone in California, but nonetheless employers are hesitant to terminate employees without cause, probably for fear of being sued.

I think it has to do with lawsuits being highly visible whereas underperforming employees are sort of an invisible cost. So, the risk assessment focuses on the rare but highly visible occurrence rather than the ongoing cost of continuing to employ someone who isn’t productive.

Just guessing. I don’t really understand this phenomenon.