Against Napping at Work
Viewed as Unacceptable
Although some companies have warmed up to the idea of naps, many have (and may always) view it as unacceptable. They would rather be seen as working diligently than passed out in the break room or office. Many industries set specific company policies to not allow napping, and even write-up employees found napping on the job. They argue that you're here at work to get your tasks done, not to nap the day away.
Sense of Laziness
There is sense of pride in many hard-working individuals of only pushing themselves further upon becoming tired. They view taking naps as being lazy and not working their hardest. They may look down on others that try to nap. This goes for employers as well; viewing work as a place to stay diligent, and sleeping should only be done at home -- despite the often long work hours making it hard to get enough sleep.
Being Paid to Sleep
Often a 15-minute nap or lunch break doesn't allow for adequate time to sleep. A workplace that schedules in naps has to figure out if it is going to be paid or unpaid. Paid naptime is not going to make sense to most employers, however it might be necessary for someone that works a night shift. This could go back to the idea of sleeping should be done before or after work, not during, unless it can fit into the work day.
Inability to Sleep Anywhere
Some employees may like the idea of taking a cat nap at work, but are unable to sleep other than at home or simply take longer to fall asleep. If taking a quick nap just doesn't work, they may opt out of the idea altogether. Although, taking a moment to lay down or rest your eyes could be refreshing as well.