It's related to the disclaimer you always see, "The characters in this show are fictitious and any resemblance to any individual, living or dead, is purely coincidental." It's a hedge against lawsuits for defamation in case someone thinks a fictional character is based on them and portraying them in a bad light, or otherwise undermining their ability to earn a livelihood.
Which I find really amusing, considering that my sister IRL is a young-adult novelist, and her first book was based directly on our family. A fictional version of me makes a couple of cameos as the main character's younger brother. And yet her book still carries that disclaimer!