It doesn't happen for a couple of reasons
1) Its not politically "Sexy" and no politician is going to gain much of a reputation by eliminating obsolete laws
2) No government (that I know of) has the systems in place to evaluate, eliminate and update existing laws; probably because they were set up assuming that bad laws wouldn't be created, or that laws don't become outdated.
If I was in charge of a government I would set up a committee to review all existing laws, try to eliminate any law that they could, and to update the rest. I would also insist that all laws be written twice, once in plain language that is less than a page or two and describes the law in "spirit" and once in full legal language; the legal language would be used to ensure that the law is well defined, and the spirit of the law can be enforced. I doing these things the goal would be to be able to write the plain language version of all of the laws in the land in a small bookd (smaller than a DVD case) and for the laws to be clearly understood by everyone with a grade 6 or better education.
