Churches of Christ do not sing a cappella because we dislike other kinds of music. Most of us have as many songs on iPods as the next person. We do not lack financial means to purchase instruments or capable musicians to play them. We are not just trying to be different or stubbornly upholding a longstanding tradition. Why, then, do we sing a cappella?
While the Jews were subject to various food laws, forbidding to eat several types of food (e.g. pork), the Christian is under no such restriction today.