Why would a drug company want to be the first to discover a vaccination?
Why would a car company want to be the first to add a new innovation to its product?
Why would a food company want to be the first to offer a particular flavor?
Being FIRST shows innovation, hard work, diligence ... qualities that appeal to consumers and readers.
So if Rapp has the information first, it establishes his initiative and, over time, his trustworthiness. Who wants to be the second person to break the news and hear, "Oh, well, we read that first in Rapp's twitter feed."
Yes, that means something to editors, producers and the higher-ups in news media companies.