Why not a file edge on small one-piece keychain tools?

After receiving a new small one-piece keychain tool in the mail yesterday (a gen 3 skull tool from PockeTTools), I realized I needed a nailfile. It occurred to me that it would make keychain tools so much more useful if they incorporated a short file somewhere on one edge. To the best of my recollection, none of my little keychain tools (like the Skull tool for example) have this feature. The gen 3 Skull tool has a half-inch long flat edge right above the skull's eye that would be a perfect spot for this. Mine already has some striations in this area that have been roughly smoothed, and if they hadn't been smoothed, it looks like it would work almost perfectly as a fine file edge.

I hope some of the tool producers will implement this additional feature in their future designs.

Perhaps. I'm pretty sure, though, that the metal on any of these tools is harder than my fingernail. And, as I mentioned above, it appears some work was done to remove the striations from manufacture on the edge of the Skull tool, and if they hadn't done that, it appears it would have made a perfectly adequate file-like surface (for fingernails, striking matches on, deburring, using as a steel with a piece of flint, ad infinitum). It would be worth a few bucks (to me) to have this additional feature on the tool if it turned out to be a somewhat costly addition. I suspect it could actually reduce the cost of some tools, because they wouldn't necessarily have to smooth and polish a small area on one edge.

Now that I think about the cost issue, the cost of the gen 3 Skull tool (just as an example) is exactly the same whether the tool has the extra box-opening feature machined in or not.