Unless, of course, you happen to live in Arizona.
The science behind it is very simple: Arizona is one big oven. The last thing those desert dwellers want is for it to be 118 degrees at 8:30 at night.
History dates it back to World War I in 1918, where the first time-shift was implemented to save fuel. All of Arizona aside from Maricopa county abided by it by 1919. Daylight saving then ended with the war, but became permanent nationwide after the Uniform Time Act of 1966. States had the ability to opt out, which Arizona quickly did after suffering through one very unpleasant summer.