Let's put it this way, if I were to describe a particular scene in Alias from any of its three seasons, very few people would know which episode it was or even be able to describe five things that happened in the same episode (unless they watched the DVD four times). Unfortunately Alias is often remembered, even by it's fans, for individual scenes when "Vaughn looked cute" or "Sydney looked cool". That doesn't bring in many new converts, especially after a season with very few good individual scenes.
If I described a scene from let's say Farscape, many of the people that followed that show would know the plot of the particular episode, what every character was doing, and the ongoing villain or love triangle back-story that was a part of its serialized plotting.
Having a main shared focus in an episode creates an opportunity for the characters to express any evolutions the background plotting has put them through. It also tends to minimize the "I love him, I don't love him, I trust him, I don't trust him" controversy that too often substitutes for an actual story.
I think most people remember "Phase One" (Syd/Vaughn kiss, Jack captured and rescued, SD-6 destroyed) not only because of all the ground it covered (and good writing, good action) but because of the dangling ends it RESOLVED. There's no reason a big piece of that can't happen every week, both week to week and after several episodes of development.