The way the verbs systems are taught in classical Arabic is traditional method that has not changed for over 1200 years. This traditional system was created to teach Arabs the classical Arabic, and not for teaching Arabic to foreigners.
 
When the Arab countries opened to other nations in the new era, this method of teaching did not contribute to the spread Arabic. On the contrary, this method provided extra obstacle for many foreigners who had serious intention to study the language. Most of the teachers in Europe and America were originally from the Arab world, and they taught foreigners the way they themselves studied classical Arabic. The result is not remarkable