I can see how you got to the conclusion you did but I think you're making the wrong analogies like the gp.
The penny you pick up on the street, despite any argument to the contrary, hasn't been put there for safekeeping. It's lost and it's value is so low that it's immaterial if you return it or not. Actually the loss in productivity and the impossibility of the task is such returning it, unless you saw the person who dropped it, is probably a negative thing.
Now if that was $65000 then you might keep it because you can and it benefits you, but the ethical thing to do is to attempt to return it to its owner.
Compare that to a weak password though, as far as you know it isn't even lost. You're just assuming that it will be stolen so it might as well be you. Do you feel the same way about the contents of other peoples houses? Pretty much anyone who wants has the ability to enter your home, we don't do that because of ethics.
You or I don't enter others' homes because of ethics, but I think lock companies bear out my point. There are a lot of technically questionable lock products out there, but people still buy them and companies produce them.
Because most people feel even a bad lock changes the ethical calculus. Because ease of transgression has a direct bearing on the actually realised ethical result.
The issue with the original "that's not ethnical" comment was not "Yes it is" but rather "You're right, but how is that relevant to this discussion?"
The penny you pick up on the street, despite any argument to the contrary, hasn't been put there for safekeeping. It's lost and it's value is so low that it's immaterial if you return it or not. Actually the loss in productivity and the impossibility of the task is such returning it, unless you saw the person who dropped it, is probably a negative thing.
Now if that was $65000 then you might keep it because you can and it benefits you, but the ethical thing to do is to attempt to return it to its owner.
Compare that to a weak password though, as far as you know it isn't even lost. You're just assuming that it will be stolen so it might as well be you. Do you feel the same way about the contents of other peoples houses? Pretty much anyone who wants has the ability to enter your home, we don't do that because of ethics.