They probably read a book about it and thought they were instant experts. Starting a fire using a bow is hard to do and takes lots of hands-on practice and experience. I managed to do it exactly once, after hours of trying, and I had blisters that lasted for 3 weeks afterward and probably burned 1000 calories in the process.
A disposable lighter or even a book of matches is ever so much easier to put in a little belt emergency kit than all the junk you need to start a bow fire (the right wood (dry of course but not too dry), cordage, tinder, a base, a knife (to cut the notch you need to catch the coal), etc.
If you insist on roughing it and starting a fire using primitive means, use a rub stick (watch Tom Hanks in "Cast Away" use one), or even the lens from your eyeglasses or a discarded bottle.