It seems to depend on a few factors. Like is the person previously unknown, or already sort of famous? If you’re a former president publishing a memoir, you can’t really change the name of your chief of staff when telling the tale of that one time you guys were in the Oval Office and something happened. Not only will everyone know, but the story looses potency. But if no one will know who the person is, and it’s not really relevant, and you want to protect them (or protect yourself from their wrath), then sure. If you’re unknown, I think you ask the immediate people around you if they want an alias or not. The rest, you probably change because it’s easier for everyone that way.