Why are Hindu Arabic numerals more popular than roman numerals?

Answer 1

The Hindu-Arabic numeral system contains a 0 symbol which makes arithmetical operations a lot easier whereas the Roman numeral system does not have a zero symbol thus making arithmetical operations a lot more difficult.

Answer 2

It is much easier to do pencil and paper arithmetic in the Arabic system than in the Roman. Fibonacci of Pisa (1202) wrote a popular book that converted the merchants in the Italian city states to the Arabic system and it became the standard.