It's a matter of defaults, and no choice of default will work for everybody.

I agree that "rsync --archive" ought to preserve extended attributes, same with creating a tarball. But when copying a file, as opposed to creating a backup/archive, I don't think extended attributes should be included by default.

And yes I've also had to compile custom versions of rsync at one point to get a version which understood extended attributes on Mac, but I think that's mostly standardized now.

EDIT: Also most programs don't even preserve permissions/ACLs on copy, so not sure why they'd preserve attributes by default.