You're right, people shouldn't need special days, but that's the way of the world at the moment. We are currently divided based on these things. Plus, men suffer things which women don't, and visa versa. It's important, now that society has changed in fairly drastic ways, for men to have their issues discussed; because men are as equally important as women.
Maybe it's just me, but I don't get the point of that kind of International <insert_anything_here> Days.