I feel like I have a weird relationship with these command line tools. They're obviously powerful, and grep in particular can be a huge time saver to be able to quickly process a file.
Whenever I think Sed or Awk would be correct for a problem, I find myself with a clever 1 liner an hour later I look at and think "I should have just used python," as it's untestable / unmaintainable, and I'll come back the next day and not be able to read it.
Are there people out there for whom these tools are daily drivers that are actually part of their core toolset, or are these mostly just hobbiest things where it feels neat to know. Like HAM radio operation.
I sorta, kinda agree. Tools written in AWK (and friends) are indeed somewhat unmaintainable, but they're really close to being just right for a LOT of applications. The vnlog toolkit (https://github.com/dkogan/vnlog) adds just a little bit of syntactic sugar to the usual commandline tools to make processing scripts robust and easy to read and write. This was not my intent initially, but I now do most of my data processing with the shell and vnl-wrapped awk (and sort and join, ...) It's really nice. If you write stuff in awk, you should check it out. (Disclaimer: I'm the author)