Who doesn’t love a nice vacation? American workers, apparently.

A new report shows the average worker only uses half of their time off and paid vacation each year.  What’s more, three in five workers (61 %) admit to doing some work while on vacation, and 75% of workers aren’t using up all of their time off, the survey from  online career resource Glassdoor finds.

Fifteen percent of workers say they have not taken any vacation in the past year, and 40% say they’re take off only a quarter of their allotted time, or less.

Rusty Rueff, Glassdoor career and workplace expert, says workers are still suffering from a post-recession hangover. “When we first started asking this question in 2009, we got a startling number of responses of people saying ‘If I leave I will get laid off,’” Rueff says. “No one would take a vacation back then. Today, there’s a reticence that is part of it.”

He adds that workers have more vacation time than they did 50 years ago. “They think, ‘if I can bank a bit of it for insurance that is a good way to go’” he says of workers’ mentality of taking less time off to protect their job.

Respondents reasons for staying at their desk vary:  One-third say that no one else can do their work, while 28% say there’s a fear of getting behind by taking vacation. The survey also finds 22% have complete dedication to their company, and 19% say they want a promotion.

“While employment has come back, companies are not hiring at the level they were before,” Rueff says. “So there is a fear that no one else can do what you are doing, that you are letting people down or that there may be repercussions for you.”

Some workers are using their vacation days to find a new gig. Glassdoor finds that 1 in 10 workers say they have used time off to interview for another job, with 18-to-24 year olds doing this twice as their older colleagues at 20%.

And when workers do take off, they aren’t necessarily unplugged. Twenty-four percent were contacted by workers about a work-related issue, while 20% heard from their boss. Seventeen percent say they have a difficult time not thinking about work.

Becoming completely unplugged from work is becoming harder with smartphones, Rueff says.

“We laugh about it because when you are on the beach taking pictures and posting them to Facebook (FB), you are only one thumb stroke away from work,” he says. “Anyone with a mobile device can get connected to work via email.”

Of those who are working on vacation, 9% say their family members complained they were working and 6% admitted to consuming alcohol while working on their time off.

Follow Kate Rogers on Twitter at @KateRogersNews