A lot of times I have seen well-respected members of this community edit posts (including mine) changing things like "ZFC" into "$\mathsf{ZFC}$".
It kind of makes sense, because formal systems like ZFC are almost universally considered to be mathematical objects.
Why, then, not just put dollar signs before and after "ZFC"? I mean, there is definitely a difference between:
I have seen 10 proofs of this theorem.
and:
The number $10$ is divisible by $2$.
What is so special about \mathsf{}? Is it common in the literature to use this font to denote formal systems?