The beauty of unwritten rules is that they are shaped by nothing more than common sense and the society which upholds them. I respect and even like these rules so much more than anything the legislators come up with. Sometimes it seems like they pass laws simply because they can, and only rarely do they admit they are in the wrong (thankfully they did in the case of the stinky knife law, at least now we no longer risk jail time if we for some reason happen to carry a box cutter around).
Stripping us of the option to administer common sense does nothing but belittle us and turn us lazy, or even defiant. And the funny thing is that rules that don't make sense never make it to the sanctity of the unwritten ones. One of my favorite unwritten rules are how no matter what, you never use the horn on funeral processions or horse drawn carriages. And. No matter how much he slows you down, you never ever use the horn on the hot dog vendor.