Given that Atlasian labor laws give employers little choice but to accept the demands of labor unions or totally shut down operations due to a strike (which they have no way to deal with due to the ban on hiring replacement workers under any circumstances). Enabling union to monopolize representation in an entire industry would enable said unions to conduct industry-wide strikes which, due to the aforementioned ban on scabs, employers would have no way of dealing with. In other words, unions would essentially be able to shut down entire industries at will. This potential for disrupting production to such a radical degree would create massive economic uncertainty (nearly every business is put on unsound footing when the production of the goods it sells could cease at any moment, and investing in capital projects, starting/expanding a business, etc all become much riskier as well), and be terrible for consumers who would have to deal with entire categories of products disappearing from stores while unions elected by as little as 51% of workers in an industry imposed their arbitrary will on millions of people.
So why don't we give employers their power back and restore balance between labor and management.