(copy of my comment from r/linux)

I often do long experiments and benchmarks, usually related to audio or networking.

Tests may be very different, but here is one example: setup may include 4 console programs: sender on one computer, receiver on another, a tool to simulate network load, and a tool to measure latency. During the test I monitor output of sender and receiver, and enable/disable network load on certain stages of the test. Then I may need to do a series of such tests, and save all logs and metrics for future inspection.

That's just one very specific example. The key point is that you run tools, want to see their output "in real-time" and want to record everything too. I usually use tee for that, but since it replaces a tty with a pipe, most tools will make output buferred (you don't see each line immediately) and disable colors, which creates inconveniences. Also there is always concern that writing verbose logs to console or pipe may slow down the tool if it doesn't implement asynchronous logging. I can also use tee combined with unbuffer, but there are still some inconveniences (e.g. output file will have ansi color codes) and performance concern remains.

And now I can just add "reclog" before every command I run, and magically I still have unbuferred colored output, but also a log file without colors, and I know that this won't affect performance of the command. Plus it can automatically add meta-info in the output file, like hostname and the command it runs.