Thanks, we understand your point of view, and definitely choosing defaults is difficult to do. We will evaluate your suggestion, but please understand that it may be difficult to change, since it could be considered a breaking change to the API (many customers no doubt rely on assumptions of the current behavior at this point).
An error occurred while saving the commentNO nAME commented
So, if it's the other way, & they don't delete boot disks, it would leave lingering disks in users projects, charging them for their usage without them knowing. It sounds pretty scummy to have a default like that where Google benefit from users in-experience. Usually when people delete machines, they wouldn't imagine the disk as a separate entity which they need to delete when all they did to create the disk was to only create the instance. I'm not affiliated with Google, just a passer-byer playing devils advocate