The issue as I see it is that there's a certain non-zero chance of getting your account suspended from service x or y, sometimes for reasons that are not common

The issue as I see it is that there's a certain non-zero chance of getting your account suspended from service x or y, sometimes for reasons that are not common sense or self-evident. Considering how integral Google Drive and Gmail are to many people's workflow, it isn't good that you are forced, in effect to take on more risk by having so many services linked to it. As an example, there were cases of people losing access to Gmail after signing up for Google+ with a birthday that was too young to comply with the G+ TOS. Another example - it is fairly trivial to get an Adsense account suspended by using a script to commit click fraud against the target account. Similar things can be done to an ad-enabled Youtube channel. It's not outside the realm of possibility at all that a third party could cause you to lose access to your email account through one of these methods if your accounts are linked.