I use two Chrome profile, one for work and one for personal. I keep them separate by not logging into personal account in with the work profile etc.
Whenever I open Dropbox Paper with my work Chrome profile, it shows to have access to my personal Dropbox. These two are separate Dropbox accounts with separate emails associated to them. Yet, I'm able to access them since I sync a shared folder from my personal account on the same computer as the work Dropbox account (Work Dropbox account being the account thats logged into on the computer).
Seems like UX overtook security in this aspect since I didn't explicitly want to "connect" both accounts outside of shared folder.
I got my first professional contract on a "Who wants to be hired?" over 5 years ago! I didn't have any professional experience and was a junior dev at the time. I met my current employer because of/during that contract as well.