Do I really have to celebrate cake day? I missed out on my first Cake Day.
Is there a reason why you didn't care about the day?
I just didn't see any reason why I would be sad about missing it.
It looks like some people celebrate Cake Day because it marks the first day they joined Reddit, but it's okay if you didn't want to mark the occasion.  However, if this event was important for other people around you, then you should be there, just to avoid disappointing them.
What about the people who didn't care about it. Aren't they more important than people who did?
I don't know who is more important but usually it is rude to fail to celebrate with others.