why do we need to celebrate a father's day and mother's day?

i don't think that we need to celebrate such days, but for many it is a day in the year to let your parents know that you aprecieate all they have done for you in your life and to let them know you care. i do not tend to go in for all the commercialism of such days (all the cards and pressents ect) but i do get one card and a small gift for my parents each year, well they are kind enough to get me something for my birthday lol. i think of it in the sense of: they helped me come into being, nurtured me and raised me well, so they certainly deserve the thanks at least once a year !