Holidays are memorial data in honour of specific historical events. The ones are very old and come from the ancient times, but the others are quite young.
The first reason to celebrate them is to remember both our predecessors and the features of the antecedency. That also shows our respect to the people who took part in the historical process.
Apart from that, holidays let us learn more in the field of history. Spending the time in our family circle with the nearest and dearest, we enrich our scope. The elders usually share their knowledge of life, and the youth listen to them with interest. In this way traditions and customs come down from father to son.
At the same time, this is less typical of the majority of modern families. Nowadays, when young people form a Family, they try to get their own place of residence. Then the newly married couple get absorbed in upbringing of children or making a career. That is why family parties become more seldom.
In addition, there are many holidays which have become less popular with the course of time. Probably, people think they do not accord to the modern lifestyle.
Finally, holidays are unique parts of the past centuries. From my point of view, we should not forget about them, since these data represent the history of the previous folks and generations.