I am not sure about the scalpel blade.
I do have a couple of ideas though.

I think the big reason is the foil packaging and that it is very small. Any single edge blades I ran across were only protected by a cardboard folded around them or came in plastic boxes. They soon worked loose from the card and then I had a loose razor blade on me, and the plastic cases were too bulky.
The scalpel blades stayed safe in the package.

Another point is I can get scalpel blades in high grade stainless steel, which means they don't rust like the razor blades I tried did. Rust is one of the reasons that exacto blades don't work well in a survival kit either.

About utility I tend to agree with the comment that they are awkward.
I found the best improvised handles were plastic. If you heat the plastic up until it is melting and press the scalpel blade into it you can get a fairly solid connection.
Toothbrush handles or even a plastic pen will work.
(I really do not expect to be doing surgery or cutting down trees with them.)

I only have #11 scalpel blades in my FAK, and the only reason they are there is for lancing boils, digging out splinters, and stuff like that.