I'm with whoever said that paracord isn't a good choice for backpacking. Too heavy and bulky for use as cord, not strong enough for use as rope. So IMO "what it can be used for" is car camping or various things around the house. Or parachuting, of course, though I wonder if they still use paracord for the risers? Probably not!

For a lighter, less bulky cord option it certainly is good to have some, and "how much" depends on whether you expect to hang food with it or not, and if so, what you're protecting your food from (bears, or rodents).

As wandering daisy said, sometimes extra cord for tent/tarp/whatever-shelter stuff can be useful. Some limited repairs (to include shoelace replacement, but I find that I replace the shoes before the laces go). Infrequently to hang food. For 3-season backpacking, that's about it for me.