You're right! I just went with an example that used to be the most relevant to me personally (the "work visa" part, fortunately not the "abusive employer" part)

You're right! I just went with an example that used to be the most relevant to me personally (the "work visa" part, fortunately not the "abusive employer" part). Let's throw in one more reason: health insurance being tied to current employer also means people may be forced to stay, at least until they line up their next gig.