In other words, there's a certain sadness to International Women's Day...which is that it has to exist in the first place. It's existence reflects the sheer lack of confidence that women have in ourselves overall. Maybe if society acknowledged the contributions of women to this world as worthwhile in the everyday, like it does those of men, we wouldn't need to have a special day. That is all.
Lots of things don't require special days, but it turns out that people just like having them for various reasons. Do we need special days to celebrate our mothers and fathers? Not really. If you had/have good parents, chances are that once you pass a certain age, you're always pretty appreciative of what they've done for you. Nevertheless, it doesn't hurt to have a day set aside to remind us to SHOW that appreciation.
People absolutely do acknowledge the contributions of women. Doesn't mean there can't be an international women's day.