In the development process, it's not uncommon to be told that the story should be from your hero's point-of-view. However, this doesn't necessarily mean that the hero should be in every single scene. It's more to do with the narrative POV of each scene. In other words, whose scene is it?
Who wants what from the scene? What do they have to do to get it? What's in their way? What do they do, if anything, to overcome this conflict?
Essentially, these questions are a microcosm of the key attributes to a good story.
One of the bigger drawbacks to the spec scripts that I read (whether it be for the Red Planet Prize or individual notes, or whoever), is that when the action cuts to a subplot, and the protagonist isn't present, the scenes lack a decent narrative POV. They deliver exposition with no real purpose, or talk about another character to push the exposition/story along (something David Mamet famously warned against in his writing memo to his TV staff: "LITTLE" EXPOSITIONAL SCENES OF TWO PEOPLE TALKING ABOUT A THIRD).
Let's look at Drive, the noir thriller written by Hossein Amini, directed by Nicholas Winding Refn and starring Ryan Gosling. The reason, I think, the film works so well is because Mr Amini knows what he's doing with the basic elements of each scene.
Take for example this early scene between Shannon (Bryan Cranston) and Bernie Rose (Albert Brooks), as they meet to discuss the Driver (Ryan Gosling). In the low budget or B version of the film, the scene would be a dull exchange where Shannon would tell Bernie about this great driver, and he's really got to meet him, etc. Instead, well, have a read (if the scene doesn't pop up on your reader, visit the blog direct or download full script here):