Excerpt from Annihilation of Caste by Dr. BR Ambedkar :

Ask Mohammedan or a Sikh, who he is? He tells you that he is a Mohammedan or a Sikh as the case may be.

He does not tell you his caste although he has one and you are satisfied with his answer.

When he tells you that he is a Muslim, you do not proceed to ask him whether he is a Shiya or a Sunni; Sheikh or Saiyad; Khatik or Pinjari.

When he tells you he is a Sikh, you do not ask him whether he is Jat or Roda; Mazbi or Ramdasi.

But you are not satisfied, if a person tells you that he is a Hindu.

You feel bound to inquire into his caste. Why ?

Because so essential is caste in the case of a Hindu that without knowing
it you do not feel sure what sort of a being he is.