While there are easier ways, it is always good to have a backup.
About the comments of "it might not work", why not try it out before you go?. Any gear that you plan on using should be tested. Who would go out into the woods planning on starting a fire without knowing the basics of how to make a fire? Who would go out on a road trip without having learned to drive a vehicle?
One problem with firesteels is for people who don't know how to use them, or are expecting the magnesium to do all the work.
cotton balls with vaseline are a good last minute method, but I would rather teach and learn primitive methods for emergency use for those "just in case" situations.
I've had a magnesium stick with flint for 20 years and I'm only now really exploring how to use it correctly. Is it possible to get a fake or poor quality one? Yes, just like it is possible to get fake or poor quality other gear (I'm thinking of the Petzl Gear thread). So just be careful. I rarely use the magnesium side of it. It often just isn't necessary. The magnesium is for wet weather where it is harder to find dry tinder that takes a spark.
Oh and don't throw out your old lighters, they still can be used when they run out of fuel. They have a ferrocerium rod in them. Check out this video.
It shows that starting a fire with simple cotton balls (can be done with other tinder) can be raelly easy.