Frankly, I missed the option, and usually I am pretty good with noticing if the defaults are what I want. The only reason I even noticed that "delete" was not actually deleting mail was that I had to search through All Mail one day, and I noticed some messages that I was sure I deleted. What makes this worse is the completely counterintuitive nature of deleting messages from All Mail: they just come back. I suppose it should have occurred to me that this is a setting I can change, but considering the other oddities I have seen in GMail's IMAP support I just jumped to the assumption that it is another weird "feature."
Really though, the point still stands: Google was not considering protecting its users from government surveillance to be a priority here. They probably had other reasons, maybe even well-justified reasons, for the defaults they chose, but those reasons only make sense in the context of their engineering requirements.
"Also, I hope your email client does secure deletes on local disk by default."
I do something better: whole disk encryption. Actually, since I use an SSD now, "securely deleting" anything is non-trivial; it is better to just negate the need for it by never storing plaintexts anywhere.
However, the option is there, and you're a person who notices if the defaults are what you want but didn't read one of only three options presented to you when enabling IMAP, basically the only settings that were even important if you're not using web mail. It's possible that the options screen was different when you originally turned on IMAP, though.
However, because of the historical lack of an "archive" IMAP function, it's still not clear that the default isn't the correct one for the average user, just like PGP on by default with private keys managed by the user wouldn't be the correct default because most users would be locked out of their own email within the week.
The lack of an "archive" function is pretty easy to fix: create an "Archive" folder. That is basically what "All Mail" is, at least for me.
The problem with this default is that it makes no sense. Most email clients already have an option to "delete" mail by moving it to the Trash folder (which Google has), and most users expect that deleting something from Trash means deleting it for good. I am just not seeing the use-case for someone wanting to "delete" a message from Trash or All Mail just to have the message reappear in All Mail (why on Earth would anyone want a message deleted from All Mail to come right back to All Mail?!).
Really though, the point still stands: Google was not considering protecting its users from government surveillance to be a priority here. They probably had other reasons, maybe even well-justified reasons, for the defaults they chose, but those reasons only make sense in the context of their engineering requirements.
"Also, I hope your email client does secure deletes on local disk by default."
I do something better: whole disk encryption. Actually, since I use an SSD now, "securely deleting" anything is non-trivial; it is better to just negate the need for it by never storing plaintexts anywhere.