You do realize that in 10 seconds your computer can achieve a lot of stuffs right?

I don't think a webpage can read clipboard without the user manually pasting.

If there's some malicious desktop program running on your machine at the same time as the password manager then you're probably screwed regardless of whether the password passes through the clipboard - but maybe there's some subtleties I'm missing here.

I've accidentally pasted sensitive passwords enough times that I know the procedure is prone to errors.

If I have to do it, I immediately copy something else right afterwards, to avoid an accidental paste later on.

10 seconds auto-clear (which is configurable) is short enough to prevent me accidentally pasting onto some other site.

Could be better if it auto-cleared after a paste, but not sure how feasible that would be.

For example it could just read all the passwords from the password manager's UI.

Between Keepass, 1passwword, and lastpass I've never seen a password manager that just shows the password without the user explicitly choosing to reveal it

1password has the option to do so and I do it on my home desktop computer. Obviously on mobile devices it would be a bad idea and on those I leave that option in it's default, disabled state :)

The purpose of clearing clipboard is so you don't accidentally paste it into a chat window or something. Not to protect against malicious programs.