There are other reasons as well. The body responsible for enforcing a particular law can choose not to enforce it, thereby rendering the law useless. Or a law c

There are other reasons as well. The body responsible for enforcing a particular law can choose not to enforce it, thereby rendering the law useless. Or a law can become obsolete by changes in technology or society - the original law legislates something that just doesn't happen any more, say. Laws can also be written to handle a specific event that only occurs once. Once that event has passed, the law might as well not exist. It doesn't need to be repealed because it just doesn't apply any more. In addition, laws are typically regularly amended to handle new societal developments, to clarify wording, or to fit better with other laws or changes in attitudes. A law that has gone 150 years without being amended at all is probably a law that falls into the categories above and is obsolete. Of course, all this is getting somewhat off-topic, but the point is that laws absolutely can become outdated and unmaintained, either deliberately or by happenstance. And the inverse is also true: most laws that people deal with regularly are kept up-to-date to ensure that they still reflect the needs and wills of the society they're being used in.