The Celts had a very well defined civilization in which women were equal to men and even held their own property (after marriage they still held rights to it).  This strong social order placed as much importance on harp entertainers and artisans as much as it did on warriors.  Placing this much importance on culture was the strongest way to instill their rich history and beliefs from the earliest of ages.  Who didn't like music as a child and is still nostalgic about it today?  These early impressions were reinforced through their entire development into adulthood and lasted a life time.   

It is in Ireland that the Celts endured the longest, even after wars with the Tudors and at last the devastation by the Cromwell.  But it was the Romans that pushed them back, destroying the Celtic influence.

The beliefs and close knit social order were so strong and important to their core beliefs that today their culture and language are still with us.