> *her, but correct.
Sorry.
> I don't think a compromised device, and thus access to local data and potentially your password manager, is such an unusual situation
Right, but what I meant is that it's unusual to have unique passwords for each service *and* have them memorized/not stored anywhere (well, sufficiently long and unique that if an attacker knows a few of them, it doesn't help him guess the others).
That's not what the vast majority of people do.
> that all said its fairly easy to remember a 20-30 length unique password if you use a passphrase and only have a couple places that are "that important" such as banking, broker, icloud, email, etc. everything else can go in keychain
Many of these services don't allow such long passwords where you can use passphrases. For example, both of the banks I use (in two different countries) only allow a fixed size 6 digit numeric password. Somewhat strict password length requirements are not very unusual.
> obligatory https://xkcd.com/936/
While funny, the problem with this xkcd, besides the password length problem, is that 1000 guesses per second is way, way, way underestimating how fast you can crack passwords nowadays if the service uses password hashing algorithms that are still commonly used. Billions to hundreds of billions of guesses per second is more in line with the right magnitude, given a couple dozen GPUs which can affordably be rented in some cloud service.
When you need to memorize passwords or passphrases for two to four services, you're already in the same entropy requirement ballpark as having to memorize one bitcoin seed (i.e. 128 to 256 bits, depending on how paranoid you are) and therefore you run into the same dilemma: if you can memorize it long-term, it means you don't have enough entropy, and if you have enough entropy, it means you can't memorize it long-term (easily/reliably).
Which is why all but the most clueless or the most paranoid (or those who can afford to lose it) store their bitcoin seed somewhere more permanent than their brain [1] -- unless, say, you only do it very carefully and only temporarily, e.g. if you need to cross a border with a large amount of BTC and you really don't want to attract attention, no matter how scrutinized you'll be (and even then it's probably much better to store the seed somewhere in some creative and imperceptible way).
[1] Bitcoin brainwallets were a lot more popular many years ago, but nobody recommends them anymore due to their severe problems: https://en.bitcoin.it/wiki/Brainwallet