This is an excellent way to limit tracking data pollination across web services. You can use your cloud mail at home and at work simultaneously and without fiddling with profiles. You can shop in the Shopping container and not have the items you looked at populate the ads you see on other websites afterwards. You can run a casual news browsing session in a dedicated container and not let various websites you visit correlate too much about you, or the web giants that track your account's activity learn that you were really into that Taylor Swift story ;)