Why can't we get a world patent?

Patents are granted by various countries, not by any international institutions. According to the public information inquiry, the EU will soon change this situation, and may grant patents in Europe. Even so, if you want to obtain patents on a global scale, you still need multiple jurisdictions to approve applications and grant rights. Patent application procedures can be simplified and unified, just like PCT procedures, but the patent laws of different countries are different, which leads to the inability to unify patent granting procedures around the world.