Fire starting kit is tiny and weighs very little even if its just a box of matches or a lighter, yet can potentially provide so much for so little carry weight. Starting fires in good weather is a doddle, it gets much more difficult in difficult weather conditions such as heavy rain, snow and windy conditions where trees find it difficult to become established such as above the tree line, so shelter and insulation become a priority, i.e. a good sleeping bag and bivvy, basha or tent. This is also why lightweight cooking stove systems exist and are commercially available.