An hour gained, an hour lost

For those who don't know, Arizona doesn't participate in "falling back" or "springing forward" like most of the country. I really couldn't tell you which is better - having to remember to change the clock or having to remember that everyone else changes, but you. All I know is that during the winter, I'm one-hour away from my family in Arizona and two-hours during the summer. 

So this begs the question... why do we change our clocks at all? It seems to work fine for AZ and some other parts of the country not to make the change. It's my understanding that we do it to have an extra hour of sunlight in the morning, but what about at night? Aren't we "losing" an hour because it gets dark at 4p instead of 5p? 

Either way, I enjoyed the extra hour of sleep I got this morning. Not because I got to "sleep in" an extra hour, but because we were so dog-gone tired by 7p that we went to bed super early.