Seems that I am not alone in my quantity of choice!

Since I'm not carrying a tent when I'm on a day hike, the 100' would definitely get used in shelter construction, esp. if I am making something robust. Lots of different lashing that you can do and with the inner core, you can extend the amount of lashing material if needed. I also carry some zipties to expedite any shelter building.

Even when I'm camping with a tent, the 100' comes with me. Useful, as many have pointed out, for hanging bear bags. Also for emergency repairs on whatever may have failed. Additional fishing line. Etc... Really limited by your imagination.