If you love someone, shouldn't you care about how they feel? If you love someone and they care about a certain holiday, you can celebrate it to make them happy, because you love them, not because you love the holiday.

From my point of view , it just like birthday or anniversary . The day that celebrate which is meaningful for the linkage with people. Of course , everyday express the feeling for love through behavior is good . But when you accept the love day by day , we do not learn to treasure it and to quarrel. The Love becomes a habit.So these day are used to remain your memory, to give more and more love on it.

Abdullah
When you celebrate and support such events.It means that you should be obliged towards them,and you can't miss or skip them at all, because you were a part of those events

You can't be supportive and unconvinced at the same time,people will doubt your honesty.

Try to look at it closely 

Then how would you describe people who will be disappointed if you forgot to express your feelings in  that day by telling them how much you love them or forgot to buy them a present? I am still not convinced. 

Who created the mother's day?