答案：1. Because it can take a long time to write down large numbers with tally sticks.
2. Instead of using tally sticks, people began using different abstract symbols to represent different numbers, which was faster and more convenient for writing large numbers.
3. - **Roman numeral system**:
- Advantage: It has historical and cultural significance and is still seen in many traditional places like clock faces and buildings.
- Disadvantage: It is too difficult to use, especially for representing and calculating large numbers.
- **Arabic numeral system**:
- Advantage: It is easy to understand and use, and convenient for representing and calculating numbers, so it is widely used across the world.
- Disadvantage: (Relatively speaking) It may lack some of the historical and cultural symbolism that Roman numerals have in specific traditional contexts.
4. Whether the world should keep using Roman numerals on clocks and buildings is a matter of opinion.
- If yes: Because Roman numerals have strong historical and cultural value. They can add a sense of tradition and elegance to clocks and buildings, making these objects more culturally rich.
- If no: Because Arabic numerals are easier to read and understand. For people who are not familiar with Roman numerals, reading time or identifying numbers on buildings with Arabic numerals is more convenient and efficient.
