What made Roman numerals easy to use?

When modern students are faced with having to learn the Roman system they often wonder how on earth anyone ever found this number notation convenient for any sort of calculations. The answer is actually rather simple. Yes, Roman numerals are not great for complicated calculations. However, they were extremely convenient when they were used at the time of their origin. Imagine having to carve Arabic numerals on wood or bark. Now imagine achieving the same objective using Roman numerals. The difference is striking. All the letters used in the Roman system can be carved with a few simple cuts: I, V, X, L, < (for C), |> (for D), M. There is evidence that a similar system was still used in the 19th century, in some rural communities in Italy, by shepherds who needed to keep track of their flocks. By the way, the simplicity of these symbols may indicate that they are not related to the Latin alphabet, but are rather independent of it, except perhaps C and M, which are probably dependent on the Latin words centum (one hundred) and mille (one thousand).