Because bunch of us memorized fckgw rhqq2 yxrkt 8tg6w 2b7q8 for the very same reason back in early 2000s
I've had users use parts of lesser known poems or stories in some foreign language, because who would expect that, right? Turns out that's not what's relevant to a good password but rather whether it is in any available corpus.
If your passphrase consists of something likely to be in wikipedia you are guaranteed to get owned in minutes.
Now that I think of it, a non pirated OEM windows key would have made for a great password. ;)
Yeah, I had that one committed to memory in highschool.