Because an impersonal God implies that God flies in the face of the Bible, and especially of Jesus. I recommend that you look into Jesus, in particular, the sheer volume of historicity involving Him. In summary: only a blind fool would deny the existence of Christ in history, and only a willingly blind fool would deny that He said what is claimed by his apostles that He said. If this is so, then He was either a complete schizo, a conman, or He was really God in the flesh. The two former don't really budge well with history since the coming of Christ unless you apply really big historical snobbery. To deny a personal God is to deny Jesus, is to brush off something that is irrefutable, is to deny reason.
Further, I have a very big contention with Deism, having been one myself. And that is that it is a response to the world having accepted the parameters of the world. Meaning, that it is a justification fo God using the worldview of those who hate God. It really is not an earnest belief for most people, it is a desperate cling to comfort because one has accepted the world as told by the secular, "reason"-worshipping world. It not only denies the Bible on the grounds of these padagrims ("miracles, etc don't happen!!!!"), but it also denies a completely fundamental attribute of God as an entity, and that is sovereignty. If God exists, then He must be sovereign over the world, and furthermore it would be expected for Him to make use of this sovereignty. As you've mentioned, to suppose that the universe, which has rules, came from an unreasonable force is madness. If then, this force is reasonable, then it would not make sense that it would make something so incredibly complex just for nothing, as is tht implication of the "great clock maker" point of view.
i.e. if God exists, then it would not make sense that He be an impersonal God. Your problem, as was mine, is that you've accepted the world as described to you by those who hate God.