The rationale for daylight savings in a southern latitude like California is this:
People generally wake up, and go to work the first thing in the morning. They would like to travel to work after sunrise. They would also like to maximize the amount of daylight they get to enjoy outside of work.
This means that in the summer, all the daylight before waking up is "wasted" so you want to move solar noon forward. But if you move it too far, it'll be pitch black when people get to work in the winter, which is why you then have daylight savings to move solar noon back a bit.
If you live further south, like Hawaii, the difference in length of day between winter and summer is very small, so you can't shift solar noon around. Therefore, Hawaii doesn't do daylight savings.
If you live further north, like Sweden, the difference in length of day between winter and summer is enormous, and in the summer the sun rises at like 3 in the morning with daylight savings, and in the winter the sun rises at 10 with standard time, and the rate of daylight change around the equinoxes is huge, so the effect only lasts a week or two. It makes absolutely no sense to have daylight savings there, and the EU parliament making it not mandatory for countries is a step in the right direction, i.e. abolish the useless thing in Sweden.
Spain and the other Mediterranean countries could maybe keep it for all I care, but Spain has a weirdly skewed solar noon anyway...