It happens. When I was an intern at PBS ten years ago, we used to have both live people and puppets in the studio for the pledge drives we used to do - I was a puppeteer for the last three pledge drives we did, but the live people were veterans who had been on-air personalities since I was a kid . . . but then, during our last pledge drive, they were all pretty much being phased out, and instead, they brought in a group of teenagers for on-air duties - the higher ups at the station said it was because they wanted to show that kids actually care about what they watch and that they support PBS. By that time, we were losing pledges and they were pulling all kinds of last resorts to try to boost slumping pledges.