I think for me, I haven't needed to use the magnesium to start a fire when I use the ferro rod method. Like most things, preparation before starting leads to greater success. The fatwood is my cheat in case of very damp wood.

I gather tinder when I see something good and stick it in a ziploc to keep dry. Usually if things are wet, I make a bigger tinder bundle and use more knidling.

IR, my guess is you probably have no trouble starting your fires and like the magnesium for your "just in case."

Don't get me wrong IR. I am not saying anything bad about the magnesium bar. I actually have one in my backpack when I am out and about. I have just never used it other than to practice with it. I haven't even scraped a piece of fatwood for "maya dust" other than to practice too.