The practice of artifically moving the "Local Time" backwards or forwards is odd.
I had no idea of the reason, until I found a chart like this one (sourced from here).
Locally, under Daylight Savings, sunrise comes between 0530 and 0600 in June. Sunset comes between 2130 and 2200. (That 9:30 PM and 10:00 PM to people who don't use 24-hour clocks.)
Without Daylight Savings, sunrise would come before 0500 in the morning in June!
I think that the American culture has decided that it is better to tinker with clocks so that sunrise is after 0500 in the morning. Even if the price is long, late summer evenings in June. And if there is a lot of hassle and dislocation during one week of Spring and one week of Fall.