Sure the shortening and lengthening of the day does have some kind of effect, but it's a gradual thing over the course of the year. And since the body's clock is pretty close to 24 hours it seems, if you continue to wake and go to bed at the same time, there's not much effect on sleeping patterns for most people. It's not like the DST jump that's suddenly an hour overnight (literally). That seems to really throw some people. Apparently when the time jumps forward in the spring, there's an increase in heart attacks measured in the US, but not in the fall change. Possibly due to loss of sleep. But if people just went to bed an hour early in the spring change maybe there'd be less problems.
People used to travel around the world before the airplane but no one ever experienced lag because the time change and the change (relative to their body's clocks) of the sunrise and sunset was so gradual they didn't even notice it. A day would be slightly longer coming west, and slightly shorter going east. In Around the World in 80 Days Phileas Fogg traveled East for 80 sunrises and sunsets (one of the two anyway), but for the people back in London, only 79 days had passed. Bit of a brain bender that.
The only thing I can say in favor of DST is that before DST spraying would start about 4am here. But that was before the advent of low-drift nozzles. I don't generally spray at the crack of dawn these days so it probably wouldn't matter, and I cover a lot more ground than my dad used to with his 60' rig. And before I farmed, I used to like DST in the fall because I had time to do some outdoor recreational activities after work. Now I am too tired to do any recreational activities after work in the fall.