Why do people criticize me for checking "Other" on the census?

Ok so I'm 16, I have tanned skin and two toned light brown/black curly hair amd almond dark brown eyes. In my immediate family my grandma is Jamaican Indian and my grandfather is a Louisiana Creole (Half Black and Native American, half French) on my mother's side. My mother is married to my father, who is Samoan. Taking all of this into account, I figure it suits me best to check "Other/multiracial" on census and forms and stuff. But more often than most, other students criticize me on that, saying stuff like "Whatever", "You look more like you're this or that", "Why don't you just pick one, you're not that mixed". I just don't feel like I fit into any one box. Especially when I look at the members of my family, and can tell they DON'T all come from the same ethnic and cultural background. Is it really that wrong if someone decides to check "Other"?