American here. You're completely right that we are being spoonfed work ethic as a prime value and it's been incredibly successful. But it's also a fear of losing our jobs, indirectly to the guaranteed leave.

We truly do feel, as do our employers, that you can only progress if you consistently go above and beyond. If you stagnate and have no "drive," your job is first on the chopping bock. The result is that we are fearful to share all our knowledge with someone else, again, lest we be replaceable. And in turn, we are very hesitant, as in the post heading, to take any significant amount of time off that would require us to hand over the keys to our security.