If you don’t fill in all the boxes for the House of Representatives ballot paper, you’ve voted informally and wasted your vote.
If you let your vote exhaust for the Senate ballot paper, you signal that you don’t have an opinion on who should get elected once your selected candidates have been eliminated, which basically amounts to throwing your vote away if your preferences haven’t already contributed to electing someone.
If you don’t fill in all the boxes for the House of Representatives ballot paper, you’ve voted informally and wasted your vote.
If you let your vote exhaust for the Senate ballot paper, you signal that you don’t have an opinion on who should get elected once your selected candidates have been eliminated, which basically amounts to throwing your vote away if your preferences haven’t already contributed to electing someone.