If you mean an extra password, the answer is that most people don't want to type in a password when they open their browser. Think it through and try to see the issue.
I don't see your "issue", as using a master password does not "defeat the whole purpose of password saving" at all. Many people have different login credentials for different websites (not only passwords, also login name or email) which are hard to remember which one you used where. Having access to them with a single master password is convenience.
I like the way this is handled in Opera, where your passwords can never be accessed/viewed in plain text at any time. Once your login data are stored, you can simply use them via CTRL+ENTER on the login form and the data is pasted into it. If you want to you can use a master password to restrict access to that data. And you can even set a time after which the the browser will forget that password and then asks for it again after e.g. 15 minutes.
I sit down at your computer and Opera is open. I go to facebook.com, click on the password field, press ctrl+enter. I then use the dom editor to change the field to text. Will I see the password?
You will not, because that domain is blocked in every OSI layer possible in my local setup. ;)
But seriously: Yes, of course you would. They have to be pasted in clear text. There is no other way to do this.
But that's not the point. The point is that you do not get to use CTRL+ENTER in the first place! Unless, of course, you type in the master password, which Opera will forget after x minutes (zero if you want it to be forgotten instantly). So you have a windows of x minutes after I've used the password manager for the last time to do your "DOM hack".
I like the way this is handled in Opera, where your passwords can never be accessed/viewed in plain text at any time. Once your login data are stored, you can simply use them via CTRL+ENTER on the login form and the data is pasted into it. If you want to you can use a master password to restrict access to that data. And you can even set a time after which the the browser will forget that password and then asks for it again after e.g. 15 minutes.