This is an excellent question. Let me begin by saying that in Kiyojute Ryu Kempo, we train with the full range of Oriental weaponry, ranging from the tsurugi (taichi sword), to the nunchaku (the flail), to the sai (metal truncheon), and the yari (spear). It is 100% true that normal people do not move around the world of normalcy carrying spears. Why then would we study them?
The art in our Ryu in which these weapons are studied is called Bukiho Kempo Kobujutsu. The most important part of that phrase to observe when looking to this question is bukiho—ho means principle, bu means martial, and ki means tool—thus we have the principle of martial tools. Bukiho is about taking whatever may be at hand and making a martial tool out of it—turning a mop into a staff, for example. In this observation, we have our answer.
You may not carry around nunchaku, but you probably wear a belt; you likely don’t carry a six inch rod, but I bet you touch a pen or pencil every day; you might not even know what a sai is, but you likely have familiarity with scissors. This is bukiho; not that you know how to use a series of old, anachronistic weapons, but that you can pick up any object under heaven and make it into a weapon. This is true self defense skill.