Please do not equate writers for "Everybody Loved Raymond" with those from the "Scoobydo" cartoons.
In TV, often times you come up thru the ranks. There's minor-league baseball, and, similarly, there are shows that people work on that are stepping stones in a career.
Not everyone come out of Harvard or Brown and gets a gig right away. I work in reality tv, have done some scripted things, and am still working towards that big break. The writers of "The Sopranos" were interviewed for an article, and some of them worked on cartoons years before they were hired by the class act of TV dramas. But you can bet that they were grateful for a job in TV, whether it was "Blues Clues" or writing voiceovers for the "...on last week's episode" opening segment of some reality show. Plus, "webisodes" - TV content written by & starring the people who regularly work for a show like "The Office" - contain advertising, and NOBODY gets paid to write or act in them, because (and I'm guessing here) the network counts them as promotional tools. Go figure.