There are a couple of really important reasons for taking Power Naps
Sleep Deprivation
A lot of people are actually pretty sleep deprived. A couple years ago the CDC put to some statistics showing that over 40 million people in the US alone get less than six hours of sleep per night.
Improve Energy Levels
The second big reason why people like to take naps has to do with your circadian rhythm, that built-in biological mechanism that governs the ebbs and flows of your energy levels throughout the day.
Most people experience their biggest dip in energy levels in the middle of the night, around two to four AM when they are, conveniently, fast asleep.
There is another big dip in energy levels in the afternoon around the hours of 1 to 3 PM.
The degree to which your energy actually drops in the afternoon may vary from person to person and based on different factors, including the quality and amount of sleep you actually got at night.
The fact still remains that an afternoon is a great way to deal with that dip in energy.