Regardless of its adoption, the need to do so still originates with Jesus Christ. Once He appeared, He struck history with such impact that He split it in two, dividing it into two periods: one before His coming, the other after it. Buddha did not do this, nor any of the great Indian philosophers.
This "splitting history" in two did not happen all over the world. For instance, Jews still us a Hebrew calendar, although the vast majority can also easily use the Gregorian calendar, which is the Christian or "Common" calendar Westerners use today.
Moslems, Indians and Chinese are major groups who each use their own calendars. Educated people in these groups can clearly convert to the Gregorian calendar, which is the one used for most international purposes. But, the average man in many of these groups still uses his traditional calendar for everyday living.
This is not to denigrate the importance of Jesus, but, even today there are many other calendars in use.