It's not that it's hard to remember, it's hard to type in. At least that's my experience (I use a few 16+ character passwords/passphrases). It might be easier if it's all lower-case, no numbers etc -- I'm not sure -- I've not tested myself.
But in writing the above, I had to hit backspace at least once -- something that's a bit hard to catch when you're typing blind into a password entry field, like when typing in the pass-phrase for unlocking a LUKS partition, or logging into a console session. Or even typing in a login password in a graphical login manager, like the windows login prompt, or gdm/ldm/xdm etc.
And it also takes time. Especially if you only get it right on your third attempt.
Shrug; I find it much easier to write English words than numbers and the like, but I guess YMMV. If you don't realize when you've made a mistake, it's well worth spending a bit of time learning to type properly, IMO; I spent a weekend practising and while I still occasionally typo, I know when I have without having to check. E.g. I wrote this sentence with a couple of letter transpositions, backspaced and corrected them, all without looking at the screen, just to check that it was possible.
Maybe. Then there is typing in the passphrase on Android [ed: ie using an on screen keyboard] to unlock the FDE etc. Fwiw I had a year of touch in junior high, so I do generally type pretty well - but I still end up having to type in my pw to unlock my computer a couple of times on average. I'm not sure which parts I miss - quite possibly I'd be better off with a slightly longer, all lowercase pw.
But in writing the above, I had to hit backspace at least once -- something that's a bit hard to catch when you're typing blind into a password entry field, like when typing in the pass-phrase for unlocking a LUKS partition, or logging into a console session. Or even typing in a login password in a graphical login manager, like the windows login prompt, or gdm/ldm/xdm etc.
And it also takes time. Especially if you only get it right on your third attempt.