Because, for better or worse, the Bible is essentially a marketing document (https://blog.hubspot.com/blog/tabid/6307/bid/33396/8-of-the-biggest-marketing-faux-pas-of-all-time.aspx). As such, its message needs to be clear and unambiguous otherwise people can (and will) read things into it that are not intended (or in some cases are explicitly recommended yet totally unacceptable. To give a few examples, slavery, killing your disobedient son, disallowing things like wearing eyeglasses, multiple wives, rape, infanticide…