Festivals are diverse, plenty and regular. Every culture has it's own share of festivals and each one has a story associated with it.
From a historic perspective, each festival has a very specific significance. Arrival of a season, or the victory of good over evil, or the birth of god etc etc. Celebrating the festival means respecting that event and accepting as a positive influence in our life. This in my opinion, is the reason why our elders celebrate and follow festivals with such zeal and devoutness.
But, today's time and society is very different. We do not believe in doing things just for the sake of it. And, in today's modern and competitive world, we personally do not connect to many festivals. Let me try to answer this with a current perspective ... why festivals are important in today's time.