By printf I didn't _literally_ mean printf -- I meant any logging type equivalent whether that IS printf or a built-in logging system. The point is there's no inter-op between them with any rich detail, which prohibits universal log viewers.
When I say travel over the network, I don't mean scp. I mean allow my iOS/Raspberry Pi/local Erlang server device to stream in real-time it's logs to any viewer that I want, whether that's on the same device or somewhere else in the world. That's the kind of portability required when you can't guarantee that complex display can be part of the same system that generated it -- that's a unique quality of web browsers. IT'S ABOUT THE PROTOCOL, NOT THE MECHANISM.
Text is great, and most logs will be in text. But I also sometimes want to inspect data, or expand JSON, or view an image, etc etc. But let's even stick with text -- a good viewer would let me set up filters on a host of structured qualities -- filenames, lines, log levels, keywords, etc. It would output in a way that allows me to easily view such info in a UI that supports infinite scroll back, easy copy/paste, elegantly formats so different log instances are clearly separate from each other, adds color to enhance readability, allows me to hide/collapse sections or duplicate entries, provides columns for the structured logging fields like timestamps, allow interactive sorting on these columns like Excel, etc etc all without losing my data.
Apple's Console.app is an elementary example of what I'm suggesting I'd like to see. Except I don't want it tied to the syslogs of an Apple device. I want every language/platform to be able to output to it in real-time. And for it's capabilities to be as rich or richer than what we have in the browser. We already have universal text editors like VIM/Emacs -- why can't we have universal log viewers?