It's not the driving, it's the parking. You're asking people to find a parking spot in the middle of the city hundreds of times a day, and no shit the spots just don't exist. Either they break the law or the packages don't get delivered.
Some cities have dedicated package delivery spots which help, but that's far from universal and sometimes regular drivers will abuse them. Also, they may not be located near the location the package needs to be delivered.
The people writing, enforcing and interpreting the laws don't care if the law is unfair or impossible to reasonably comply with. That is miles outside the scope of what they do.
Laws that penalize behavior that normal people frequently engage in don't get changed until the people who write the laws get bitten by them (which rarely happens for reasons outside the scope of this comment).
