Right, not strictly aviation related, and could easily verge into the political.
Here's a survey
http://www.marketwatch.com/story/expedias-2014-vacation-deprivation-study-americans-and-asian-workers-lag-well-behind-europeans-in-vacationing-2014-11-06 on vacation days workers take in the US vs some other countries. On average, Americans earn 15 paid vacation days per year, and take 14 of them. Americans are likely to use the term "vacation days" for days they take off when other members of their company/office are still working. The term "holiday" is often used for a day when the office is closed (we have 10 national holidays in the US, five of them are scheduled for Mondays, which makes for a "three day weekend." Many workers get these as a paid day off in addition to their "vacation days". There are no federal laws requiring that workers get these days off, but most do).
Some pontificating: The American workforce is among the most productive in the world, and they produce the among the world's highest GDP per capita. The labor force is highly dynamic-- private companies are free to cut and add positions
or particular workers with far fewer restrictions than exist in many industrialized countries. Membership in labor unions among private employees in the US has been declining for decades. We can debate the pros/cons of this and the reasons for it, but one of the results is that American private-sector workers are highly incentivized to perform well on the job.
Every situation is different. I'd say that among the people I work with, most of us would have said that if we didn't use all our vacation days (i.e. sold some back) it was because "I didn't want to leave important work undone," or "with the work I had, I couldn't find a good time to take all my vacation days" rather than "I was afraid I'd get fired if I took vacation". The end result is maybe the same, but the distinction is important. There are undoubtedly cases where workers are "afraid" to take a solid month off--"if they can do without me for a month, maybe they'll decide they should eliminate my position entirely". Or "if my replacement does a better job than I did, maybe he'll get my job." But, even if that happens, finding a new (better fit?) job is easier in the US than in many other industrialized economies.