Using default credentials to log into a device you do not own is often classified as "unauthorized access" under computer crime laws (like the CFAA in the US).
Manufacturers release patches to close security holes that Dorks often exploit. inurl multi html intitle webcam link
To understand why this string is powerful, you have to break down the Google search operators being used: Using default credentials to log into a device
When combined, these operators bypass standard search results to find the direct login pages or viewing portals of networked security cameras. The Risks of Default Configurations inurl multi html intitle webcam link
Some cameras are set up with no password required to view the stream.