It actually makes a certain amount of sense. There are people who have to work in the daytime, e.g. because they work outside. Farmers, construction workers, etc. Then their administrative staff needs to work at the same time as the outside workers, and their customers and suppliers need to work at the same time as the administrative staff, etc. So everybody works 9-5, where "9-5" is some approximation to daylight hours.
But changing clocks twice a year is still stupid.