They have no business model based on consumer information. Guess who does? One of their big competitors, Google, whose revenues are 90% made up of advertising, thrives on this data.
Further, privacy is obviously a hot topic, well at least in tech discourse. None of my friends are really bothered by any privacy concerns and couldn't care less if Google mines their email to provide targeted ads, honestly... But to the extent that privacy is meaningful to people, safeguarding it is obviously a benefit and thereby something one can sell, and seeing as there've been so many different scandals people probably are at least somewhat sensitive to privacy-centric marketing.
In short, they're selling a consumer benefit while taking a jab at the competition. Not a bad deal, there are barely any cons. Apple never really got into the advertising game, doesn't need to and unlikely plans to. They've had some ad products and neglected it for a long time, probably in large part because ads are a shitty consumer experience and Apple tries to offer the best experience even if that requires higher consumer prices. And finally it's completely in line with Apple's business models on content in the past, creating walled gardens to push paid content (music, books, news, apps), advertising doesn't really fit into that context.
Consider also that it's obviously in line with Apple being the 'nice guys', who recycle materials, appreciate diversity, the artists who just want to be free blabla. Businesses or governments tracking users doesn't fit that narrative and protecting users from these parties does.
And finally, I do believe they genuinely care without any ulterior motive and are willing to push for the things they care about if it doesn't hurt them (much).