The requests are not made, because some operating systems prevent this.

If you're on OSX, the permission to "discover on the local network" prevents it from happening ( System Settings -> Privacy & Security -> Local Network -> yourbrowser )

Could also be 'network' permissions on firefox ( Go to Settings > Privacy & Security > Permissions ) which is on a per site level, but iirc that could be set site-wide at some point.

The other browsers likely have similar configs, but this is what I have found.

Looks like this is new to MacOS 15 Sequoia, as I don’t see a Local Network option in Sonoma.