Why does Network Manager always ask for my keyring password?

There is an option in Network manager not to use password. If you edit the connection, at the bottom of the page there is a box "available to all users" if you tick this it will not require a password.

To edit right click the icon, select edit Connections, select wireless,select your connection and click edit.

NM does not ask for your root password! It asks for your keyring password.
Your keyring saves passwords encrypted, so no one can steal them. That is why you need to enter your keyring password, so Ubuntu can decrypt your passwords to use them (eg. to get your WLAN-Password).

You can check the content of your keyring in Menu -> System -> Preferences -> Passwords and Encryption Keys. Here you will find all your passwords in cleartext, after you unlocked your keyring (rightklick an element -> properties -> password -> show password).

To change your keyring password, rightklick the line Password: login and choose Change Password

Choosing no password will make keyring never ask for any password again, but still save them (unencrypted! So this should not be your first choice on a Notebook).

The reason why NetworkManager asks for your password is that it wants to keep your passwords in a safe place (an encrypted keyring), while ConnMan doesn't care about that...

If you don't care about security, you can remove the password from the GNOME keyring, or use ConnMan instead...

And migrating to ConnMan as the default in Ubuntu is currently no option, as it only support Ethernet and WiFi, but no modems (PSTN, ISDN, DSL, 3G), Bluetooth, VPN, etc.