You would if privacy or security mattered to you. It's a browser privacy feature to prevent somebody else's access by simply copying your browser's files to another computer or accessing them from another user account on the same system or network. If you don't care about the privacy, then yes, it can simply be an obstacle.
Actually, this behaviour is only seen in Opera. In other browsers I can see the said text, however they have other issues. Hence, I use two browsers to do one simple thing as reading a note and creating another one
And what does any of that have to do with the Master Password?
The error you're complaining about is a bug in Chromium which Opera unfortunately inherited. But a Master Password was something else present in older Presto-based versions that prevented guests from using your saved passwords at all if they didn't know the master password, and this bug in showing passwords does not prevent you from using them.
As the thread is misnamed, there are so many threads about the actual issue, and the issue is already fixed in Beta, this thread is closed.