Why Americans take only half their vacation time

Americans are lousy about taking vacations, and it's not only because the U.S. is the sole industrialized country that doesn't guarantee paid days off.

"Fear is still motivating people to not be away from the workplace," even though concerns about layoffs have mitigated since the recession, said Rusty Rueff, a career and workplace expert at employment site Glassdoor.

American workers only used half of their eligible vacation time during the past 12 months, a Glassdoor survey found. The top reason for not taking vacation time was the concern that no other employee could do the job, followed by a fear of getting behind. Seventeen percent of respondents said they were afraid of losing their job.

"There's a lot of motivation that says, 'I'm afraid of being away for too long,'" Rueff noted.

But even people who take vacation are often still working, thanks to always-connected devices such as smartphones, tablet computers and laptops.

"Couple that with how technology works, and 61 percent of people who take time off are working during vacation. You are seeing the American worker say, 'I may be out of the office, but work is really, really important,'" Rueff added.

Even though Americans are more tethered than ever to their jobs, they're also more confident about the job market and the potential for getting a raise, the survey found. About 44 percent of workers said they expect a raise in the next year, an all-time high since Glassdoor started the survey in 2008. More men said they expect a raise than women, at 49 percent to 38 percent.

While it may seem contradictory that workers are feeling more optimistic yet fail to take vacations, one possible explanation relates to the recent economic slump.

"Companies still haven't hired back to the levels they were at before the Great Recession, so while workers are more confident, they're doing the job of multiple people," Rueff noted. "There's still this fear that I'd better be good at it, so I'm recognized as a good performer."

Still, it's not as if Americans get a lot of vacation days to begin with. The typical U.S. worker at a private company is awarded 10 days of paid vacation and six paid holidays each year. That's far below what workers in France or the U.K. receive, where employees are given 30 and 28 vacation days, respectively.

While it may seem as if Americans are more dedicated workers -- that old Protestant work ethic kicking in -- the reality may be more stark. Thanks to technology, which makes it almost impossible to claim you didn't read an email or aren't available via phone, there's a growing sense of fear about taking a genuine, disconnected vacation.

"There's a constant overhang of all these fears," Rueff said. And he added, every time a worker posts a beach photo to Facebook from her iPhone, she's just "one button away" from work.