I don't know the history of delayed implementation after royal assent in all different areas, but I suppose it's fair to the marketplace to allow people to organize their affairs, which may have been in place for a long time, so that they're in compliance with the law.
For example, when a criminal provision to prohibit wage-fixing and no-poach agreements was added to the Competition Act in June 2022, it did not come into effect until June 2023—just this summer—to allow businesses that had no-poach agreements in place to get rid of them so that they weren't criminally violating the law.