To me it’s obvious how this helps their bottom line: people are very interested in privacy and willing to pay top dollar for it. Every time I turn on an additional privacy service from Apple, I feel their grip tightening on my digital identity as they push themselves even more between me and the direct relationships I have with other websites.
iCloud private relay, email aliases, and “Sign in with Apple” is their final act to completely dominate the relationship between their users and other web applications.
I’m not bitter about it, but I do think it’s helpful and healthier to view Apple in this way and not mistake their efforts as altruistic. They’re simply a company trying to develop a profitable, high retention service… and they’re doing a damn good job at it.