Microsoft is notorious for asking users to log in multiple times, even when you check “Keep me signed in”.
Now we have the opposite problem. Here I am in Office 365, logged in as the admin user:
I need a break and want to stay secure, so I drop-down the menu top right and choose Sign out:
Lo, I am still signed in:
And no, it is not just a browser cache issue or similar. You can still do administrative tasks.
I have seen references to the bug in Microsoft support forums, so it is known, but unfixed for ages.
I do not publicise this sort of stuff because of any antipathy towards Microsoft. Rather, I do it because it needs to be improved.