[deleted]
Probably best to explain with an example?
Say you want to lend your phone to someone temporarily, like a kid or a friend, but you don't want them to have access to a profile with your personal info in it. What you can do is quickly log in to the owner profile, set up a new user, then install the necessary apps, then optionally set some restrictions, then hand the other person your phone.
That or GrapheneOS users might have profiles that have particularly sensitive information or apps in them and they feel safer immediately locking down the profile and pushing apps from a trusted owner profile.