It would increase keystrokes for me because now I just use `--outdir` to put the
extensionless binary in my bin directory. If the default filename were changed
to have a suffix I would then need to override the filename for each of my
projects.

Besides it's easy enough to have a .cfg with `--outdir:build` or whatever you
want inside.

Speaking of language audiences, I believe both rustc and the go compiler produce
extensionless binaries by default.