It's impractical because you might not necessarily feel like sleeping simply because the sun is down.The invention of artificial lighting makes sleeping early impractical? It doesn't get any more practical than retiring and rising with the setting and rising of the sun. A time on the clock is entirely incidental, and if you didn't have a clock or artificial lighting, that's precisely what you'd do. I guess it's just too bad you have no control over your artificial lighting and are compelled to stay up later.
My body tells me to stay up later, not the clock or artificial lighting. In fact, in the winters when it gets dark earlier I actually seem to shift to an even later schedule.