Such is the seduction of the popular media, at least for me. Not everyone wants to write for a general audience, and not everyone can do it well. But clearly, there is a place in the academy for those who can. From a college's point of view, it is important to disseminate faculty research broadly. Many grantmaking agencies depend at least to a degree on public support for research, which means that telling the public about your professors' useful research makes it more likely that your institution will get grants.
Public support increases legislators' enthusiasm for public institutions, too.
For the individual scholar, translating academic jargon into language comprehensible to those beyond your immediate field is a humbling experience. It makes you realize how far your work is from real life, and how difficult it is to convince people that what you do is interesting and worthwhile. Using accessible language also makes academe a more user-friendly place, allowing professors and students in other fields to understand what is going on in unfamiliar disciplines. If the purpose of academic research is to contribute to human knowledge, presumably for the greater good, then that research should be accessible to everyone. Think of Margaret Mead, Jane Goodall, and Donald Johanson.