But it's not just about having access to example corp. If I log in to GitHub from my work laptop then my company technically has access to my personal GitHub account and the repos of any other organization I happen to belong to. It goes the other way around to. If an attacker hacks my personal laptop and I'm logged into GitHub then they have access to all of my companies repositories.
There are perfectly valid reasons for segregating accounts so that there is complete separation between them.