Re: S3 bucket default is *private* to that account
@ AC, it may or may not make routine stuff like security easier, that is not really the point you addressed in your post. The fact that something is made easier is of no use if you do not bother to get even the easy configuration done. I see you assume that the worst case applies until you have checked and double checked that all possible steps have been taken to secure the shop. So one brownie point for you and all of those who follow that example.
However, if Joe Thickastwoplanks Or Bertie Cheapscate does not bother to look let alone check they have not messed up; then the ease or difficulty of getting it right does not matter. The fact that AWS was said to send out reminders of misconfiguration suggests that the Joes and Berties might need to invest in some staff who can read and do some basic checking as well.