Yes it is worth it, because it is available everywhere, and will still be around in 15 years. Learn it once, use it "forever", everywhere. It's the same with learning to use sed, awk, etc. They've been around for 50 years and will most likely be for another 50.
No, very few. Sports being one of them. It took almost a year but now I like it, and miss it if I don't get the chance to exercise. Getting a garmin watch helped me stay motivated, because I could see the progress I was making. I went from running 2.5km at 7min/km pace and almost dying to running 10km at 6min/km pace and feeling great, even being able to talk during. And I feel so, so much better in general. It's like the difference between being hungover vs normal, but all the time.
It's literally scissorcutfigures. In German you can chain nouns together to make up more specific ones. Like Doppelkupplungsgetriebe. It's literally doubleclutchgearbox.
All the more reason to learn and use curl