Evil will find you, unless you remain well hid. And we are obviously to hide ourselves in the Lord Jesus. When scripture gives us a command, we are not to question it, we are to obey it. And it is dangerous to seek a reason when none is given. But in this case, God in His mercy offers us an explanation.
Sin is compared to fire in the Bible.
For just a small spark can set a whole forest a blaze. Even so the tongue is a little member and boasts great things. The more sin is fed, the bigger its appetite becomes. It is for this reason that such a beast is to be avoided at any cost. If fact, it might be better said, the cost of avoiding sin is much cheaper then the actual purchase.