Another great article Comsie! I think sub-plots are critical to any but the barest of stories. They are especially important in speculative fiction worlds. Unless you are using spaceship as background and calling that Science Fiction because spaceship... lol.
In my own writing, I use sub-plot items to tie my short stories together to the world and make the world feel lived in. My only problem is making sure I keep everything consistent. Because if I mentioned it, it ties into something somewhere. Some of things are planting seeds for a bigger payoff later on.
I think JMS's Babylon 5 show is my inspiration for story arcs and ties across different stand alone stories. There wasn't a single episode in 5 seasons that didn't have some, often significant, plot tie to the bigger picture or the characters that inhabited that world. This was up against the "planet of the week" sort of thing you got from Star Trek at the time. In fact, if you are fan of Star Trek Deep Space 9, you'll see the "Babylon 5" effect in the shows prior to Babylon 5 and shows after Babylon 5's success. The whole Dominion War story arc only appeared after B5 blazed the path. They did a good job with focusing their previously random sub-plots.