Why not git reset --hard <path>?

I was applying an old forgotten stash to see if there were any edits in
it I wanted to preserve, and my old changes to one file made no sense
any more.  I wanted to drop then all and keep the version in HEAD.

I'd been using git reset <path> after resolving conflicts, to leave
the changes in the same un-staged state they were before the stash,
so I tried using "git reset --hard crypto/842.c" to throw away
my local changes.

And I got
fatal: Cannot do hard reset with paths.

So I did "git reset <path>" followed by "git checkout <path>", which
achieved what I wanted.

But what I don't understand is why git reset couldn't do it for me in one
step.

I understand that "git reset --soft" makes no sense with a path, but
why not --hard?