For one thing, it establishes the POV pattern, so it doesn't come as a surprise and disruption to introduce another.
For another, if the events happen more or less simultaneously, this keeps them in sync. Multi-thread stories where the events in one sequence are not in the same time frame as another sequence can be annoying to work through. Which I have found true even when the final structure of the work made it the clear and correct aesthetic decision for the structure, and that's rare.
For a third, it gets the subplots rolling.
For a fourth, you can start the dramatic irony really early.
But it does have its price. Short glimpses of people, especially disjointed ones, do not inspire sympathy and identification the way concentrated and prolonged doses do. I find it harder to get into the story because I'm less concerned with how things turn out.