Chrome and Edge have some interesting "integrations" that may seem like really small details but "just work". For Edge when you install Windows 10 for the first time it will automatically log into Live.com (Outlook) accounts so a new user will open that stuff up and immediately have access to their emails, documents from word, etc.
Similarly for Chrome all of the Google account stuff is very deeply integrated. Google goes through a decent amount of trouble to trust the shit out of those cookies too. I had a laptop that was unused for 18 months with Chrome on it, when I opened it back up it was still able to access everything without any kind of re-authentication. Firefox on the same laptop needed to be re-authorized.
EDIT: Not making the argument that these are valid reasons, just that users are super risk adverse/lazy.
Similarly for Chrome all of the Google account stuff is very deeply integrated. Google goes through a decent amount of trouble to trust the shit out of those cookies too. I had a laptop that was unused for 18 months with Chrome on it, when I opened it back up it was still able to access everything without any kind of re-authentication. Firefox on the same laptop needed to be re-authorized.
EDIT: Not making the argument that these are valid reasons, just that users are super risk adverse/lazy.