Employees should not depend on the government for their ability to walk away from a job. They should depend on real assets that help them live more self sufficiently outside of their employment. This should include family, friend and other forms of community ties.
They would not really depend on "the government" as UBI would be codified in law and universally available, so government could not take UBI away from an individual or a group.
Also, we already depend on "the government" to make available (or protect) some pretty important stuff we depend on: rule of law, public safety, healthcare (in most developed countries), etc..
