This is so, so true! Most of us know a lot of fire starting methods: matches, firesteel, battery and steel wool, some chemical reaction etc. I can make an ember with the firebow. So for me, the hardest thing is not the source of fire but getting it to catch! I agree that the step from spark to a hot fire the size of your fist is just as crucial as creating the spark in the first place. Things become even harder with a colder spark like from traditional steel and (stone) flint, not to mention pyrite. Just go outside when it has rained, take one (1) match and try to light a fire with what is naturally available.
This is so hard! Training this technique is important. You have got to collect lots of wood, kindling, and a lot of fine fluffy stuff so everything is ready so you can “feed” the spark and later on the fire. You don't want to run around with a barely lit fire looking for fuel. Exercise and then exercise some more in all kinds of weather and with all kinds of materials!