There are a lot of low-hanging fruit forensic techniques that would allow for recovery of data that was once on the device and you now think to be gone, like se

There are a lot of low-hanging fruit forensic techniques that would allow for recovery of data that was once on the device and you now think to be gone, like session tokens and cookies. One of the major reasons to use full-drive encryption is so that these forensic artifacts will be encrypted in addition to the files you still actually keep around. This is also why you should enable full-disk encryption at the very beginning, OR wait while the entire drive is rewritten when you enable it.