It doesn't have to be "constant". It's enough to happen to you once to cost you tens of thousands of dollars, or your health, or, if you're very unlucky, your life. I've seen photos of people with firearms drawn stopping motorists at protests. You can talk all day about how it doesn't happen, but I've seen photos and videos of that happening. There's no way I would go to such place for $20/hr (Uber's average wage in SV, for example). It's just not worth the risk.