False
46% take all their vacation days
Most of the rest take some of their days. On average they take half their days off.
The reasons they don't take all their days: They fear getting behind on their work (34%), believe no one else at their company can do the work while they’re out (30%), they are completely dedicated to their company (22%), and they feel they can never be disconnected (21%).
What? No. From the report you got those number:
54% didn't take all their days off. Of that
41% didn't take any days. Only 23% took all their days off, but it doesn't count if you still work, and 2/3rds of those who took a day off still worked and 1/4th went into the office on their vacation. That report you cited also included this gem: “We have almost no job security in the U.S., no legal requirement for severance pay and, with very few exceptions, can be laid off without notice.” So, all those things you quoted as reasons why they don't take them can be summarized as afraid of losing their job. After all, if you get behind, you're fired. If someone learns your job, your fired. If you arn't 100% dedicated you're fired. If you disconnect they will realize they can do it without you, and you're fired.
My point stand: most people in the US (>50%) never take a vacation, as defined as not working, because they fear of losing their job.
Why do people put up with this? Because employers hold significant power over employees who are easy to replace. If you get hit by a car you will never be able to pay off the bills. If you don't have a job with benifits you have to pay for insurance. You do have a job with benifits? Don't let anyone know they can survive without out you, even if that means never taking a day off.