What if you're demonstrating a problem with a login screen? And yes, I've had to do exactly that more than once.
I wouldn't do it with a particularly sensitive password (online banking etc) but there are enough passwords I use regularly for work purposes where it wouldn't be a significant risk for others to watch me type it in, certainly if the characters aren't revealed at all while typing. Though having password fields be able to detect your screen is being shared automatically and obscure what pixels are relayed would be nice.
They're typically passwords that are only for testing accounts anyway, and that are known to the team members I'm sharing with.
But...it's easy to slip up now and then and forget you're actually putting in a password while screen sharing that it's probably best not to have your co-workers know! Obviously the worst is your actual O/S password, as knowing that could potentially allow a co-worker access to other passwords that are quite sensitive, but I'm not sure it's even possible to screen share your O/S login screen - probably shouldn't be! It is a good argument for not re-using that password for any browser-based logins, but SSO policies tend to make that impossible unfortunately. Mind you I use a pin for my O/S login screen, whereas for browser-based logins you can't.
Sadly I think security systems will have to accommodate the possibility that someone else can see your screen. And hope that they can't see your keyboard.
