How is changing code simpler than literally clicking on the line number to set a breakpoint?
Generally when I am coding I auto-run the tests on save. This means that to printf-debug I just add a message or two (and if I am coding I might already have a couple of useful ones lying around) and save. Then in less than a second I have a trace trough my program in the terminal. If I want to inspect a different variable I just add another print and run again.
With a debugger I need to kill my auto-run command, run the program, set breakpoints, type to see what variables I want to inspect, maybe switch stack frames, maybe step through a bit.
In my mind printf is like an automated debugger. I just put the info I want to see into the program and it does all of the printing for me. And when I find the problem I can just fix it and I am back to my edit-test cycle.
I'm not saying that there are no use cases for a debugger. For example I find variable-modification breakpoints very useful. As you mentioned if your edit-run cycle is slow then it may be faster to inspect a new variable in the debugger than adding another print statement. But when I just want to inspect values in my program I find printf sufficient and lower overhead. I'm sure part of my problem is that because I rarely use a debugger I am not as efficient, but I also think that printf-debugging is a very effective workflow for a wide variety of issues.
Every proper IDE has a keyboard shortcut for that though.
With a debugger I need to kill my auto-run command, run the program, set breakpoints, type to see what variables I want to inspect
This indeed falls under your 'part of my problem is that because I rarely use a debugger' statement. E.g you could set breakpoints before you save, use auto-debug instead (i.e. launch program under the debugger on save instead of just rnning it - without breakpoints there shouldn't be much of a difference unless it's one of those nasty multithreading bugs), add variables you want to see to the watch window. Or type them anyway if it's a one-time thing. Or use tracepoints. Etc.
I personally keep bouncing back and forth between debugger and printing. All depends on context, but it's definitely worth it getting to know both really well.
More fairly, it is a trade-off with the debugger giving wide visibility into state, but narrow visibility temporally, and logging giving narrow visibility into state (just what you logged), but broad temporal visibility. They both have their place, but I find that logging narrows things down more quickly, while the debugger helps me understand the problem by walking through step-by-step, assuming the problem isn't obvious once narrowed down.
We agree with your critique of traditional debuggers and Pernosco tackles that "temporal visibility" problem head on.
Debug printing also allows you to debug programs running in environments where you can't attach a debugger. For example, maybe halting the program causes the bug not to trigger. Or it's a remote system where you cannot attach a debugger for various reasons. Or the bug only happens in the optimized build, which in say C/C++ can make it quite tedious to walk through with a debugger.
Most of the time though I use print as "proactive debugging". Having detailed logs available is gold when customer calls with a blocking issue.
Showing function return values automatically was really an eye-opener when I first encountered it.