Hina-matsuri, known as Girls’ Day on March 3, is a special day in Japan, celebrating growing up. I don’t intend to explain it in detail here but, if you are not familiar with the custom, I recommend you check it out on Wikipedia which tells you better than me.
One of the reasons might be simple and easy, that is, it is very expensive and space-consuming for present-day life. Before all, such a traditional custom is gradually missing and children are sometimes not interested in it.
Hina-matsuri is not a national holiday today. It is said that it was a kind of holiday until 150 years ago. Anyway, nobody pays attention, whether it is holiday or not, because it is a Japanese custom.