They seem to be next of kin.
Why not use firesteels:
- when I started carrying mine, firesteels were not available in my neck of the woods and I desperately wanted one for EDC
- I like to play
- the gas lighter flints have a nicer size for the key ring
- I like to play
- they worked well
- I like to play

BTW: Meanwhile Germany reached a somewhat developped state and the firesteels are available. I bought some for my outdoors kits but they are little too bulky for the urban kit so the tiny flint still travels on my key ring.