When people first began constructing histrograms, a particular shape occurred so often that people grew to expect it. Hence, it was given the name normal distribution. It is what psychologists call the bell- shaped curve . Every statistics course spends lots of time discussing it.
Text books have long chapters and many exercises about the normal distribution.
I'm not sure why so much time is spent on purely technical issues, but the normal distribution is important. Some statistical techniques demand that individual data items follow a normal distribution, that is, that the population histograms from which samples are drawn have a normal shape. If the data are not normal, the results from these techniques will be unreliable. We've already seen in some cases that reporting a mean and SD can give a misleading mental picture and would be better replaced or supplemented by percentiles. Not every distribution is normal.