Why is there a double standard in the one drop rule?

Cherrylicious
I personally do not subscribe to the one drop rule at all as I do not believe in it because for obvious reasons. But I believe that there tends to be this nonsensical double standard when it comes to deciding who is considered black and who is not especially when it comes to mixed people is when people tend to be very selective of who they consider to be an African-American man or woman I'll give some examples.

Mariah Carey (considered biracial rightfully so as she is)

Meghan Markle (considered biracial rightfully so as she is)

Alicia Keys (considered black even though she is biracial)

Jhene Aiko (considered multiracial rightfully so as she is)

Halle Berry (considered black even though she is biracial)

Beyoncé (considered black despite having with Creole heritage)

Barack Obama (considered black even though he is biracial)

Drake (considered black even though he is biracial)

Tiger Woods (considered black even though he is multiracial with an Asian mother)

So why do people pick and choose who is black and who isn't due to physical appearance obviously and if we are going to one drop rule someone, shouldn't we keep it equal for everyone who is mixed with black? So if Barack Obama is considered an African-American man despite him having a white mother, then Mariah Carey should be considered an African-American woman despite her having a white Irish mother. Fair enough?
Why is there a double standard in the one drop rule?
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