This exploit is significant because it:
1. Is easy to use
2. Can be used frequently (Autofill is a common feature)
3. Can easily compromise valuable personal information

Please see https://dev.chromium.org/Home/chromium-security/security-faq#TOC-What-about-unmasking-of-passwords-with-the-developer-tools-

One of the most frequent reports we receive is password disclosure using the Inspect Element feature (see https://code.google.com/p/chromium/issues/detail?id=126398 for an example). People reason that "If I can see the password, it must be a bug." However, this is just one of the physically-local attacks described in the previous section, and all of those points apply here as well.

The reason the password is masked is only to prevent disclosure via "shoulder-surfing" (i.e. the passive viewing of your screen by nearby persons), not because it is a secret unknown to the browser. The browser knows the password at many layers, including JavaScript, developer tools, process memory, and so on. When you are physically local to the computer, and only when you are physically local to the computer, there are, and always will be, tools for extracting the password from any of these places.