How come we haven't noticed this before? That is, some of those logs were probably sent at some point to somebody who didn't exactly expect this kind of data. I'm surprised nobody found out sooner.
In the logs made public in one of the earlier HN stories, the messages and such are a small part of the log. There was a ton of crap about the phone with someone's text message buried in the middle.
Similarly, the keypress logs were in hex or something as I recall. All there and usable by anyone who knew what it was, but maybe not that obvious if you didn't know what the hell that part of the log meant.
In other words, if people were just scanning the logs for other stuff, rather than reading each log carefully, they'd probably have ignored that stuff.