Does Age Heaping Mean the Romans were Innumerate?

The system of dating years since some ancient point in the past used today by the Western, Islamic, and Hebrew Calendars among others makes it much easier to remember how old you are. If you know you were born in 1964 or 5725 and know that this year is 2015 or 5775, it's easy to work out how old you are. But in ancient Rome it seems that it was not even common to date years by the number of years the emperor had ruled, let alone since the foundation of Rome. It was more common to name years by the names of the consuls in office. So, it's not surprising that there is a lot of age-heaping on Roman tombstones. Gregory Clark argues that this shows that Romans were very innumerate. That might be partly true, but the lack of a proper dating system also needs to be taken into account.