Face Unlock for apps? I don't have any apps I use that need my fingerprint or Face.
Really? I have at least a dozen, likely more than can authenticate using FaceID instead of me manually inputting a password. Most importantly, every time I fill-in login credentials to an app or website using iCloud Keychain or 1Password, it verifies using FaceID, else I’d need to manually enter a password every time. I likely use this functionality dozens of times per day.
As @Awesomesince86 mentioned, password manager integration is much more seamless on iOS and one of the primary reasons I use it day to day over my Pixel 3XL.