The idea has been around a long time. Making it practical has been a much more recent development. Ideas are cheap. If you're using logs, you're using a debugg

The idea has been around a long time. Making it practical has been a much more recent development. Ideas are cheap. If you're using logs, you're using a debugger, just a very limited one. Reasoning about a program statically is great, but once it gets above a certain size you can't keep it all in your head and you must collect data to narrow down the problem. That's where a debugger comes in. Then there are the cases where you're debugging someone else's code and you don't have it in your head in the first place.