The password prompt (for example for gparted) blocks the screen and does not allow the user to interact with other applications. I think the password prompt should only block the current window. If a user stores passwords in a password manager, he may have to look them up before he can enter them.
It is also a matter of control over your system. Microsoft's Windows does similar things when asking for permissions to install a new systsem or installer are blocking the complete screen. This does not leave the choice to the user. I am doing several things at the same time and suddenly everything is blocked because ONE application needs a password. This behaviour should be changed somehow.