Agrarian cultures built their societies around sunlight, waking up with the sun to toil in the field and heading home as the sun lowered beneath the horizon. But the industrial revolution brought with it the freedom to unshackle us from nature's clock.
As long ago as 1897, countries around the world began instituting daylight saving time, adding an hour of sunlight to the afternoon. This meant communities could be more productive — people could work longer, and when work was done it was still bright enough to run errands and stimulate the economy. The added daylight also meant more exposure to vitamin D and the added time for people to exercise outdoors.
However, this has changed a lot since then, as most Western countries has a small agricultural sector (less than 5%). Lighting can be obtained much more efficiently than in the past (e.g. LED bulbs).
There are several pros and cons related to DST covering energy usage, economic effects, public safety and health. However, it is clear that it affects the the Circadian Rhythm and adds some complexity for time computations, as DST is not uniformly applied.
Question: Why is Daylight saving time (DST) still used in so many Western countries?