Non-Hindu castes are counterbalanced by integrative ties absent among Hindus.

Evidence

If we apply these considerations to castes among Mahomedans, Sikhs and Christians on the one hand, and to castes among Hindus on the other, you will find that caste among non-Hindus is fundamentally different from caste among Hindus. First, the ties which consciously make the Hindus hold together are non-existent, while among non-Hindus there are many that hold them together. The strength of a society depends upon the presence of points of contact, possibilities of interaction, between different groups which exist in it. These are what Carlyle calls “organic filaments”—i.e., the elastic threads which help to bring the disintegrating elements together and to reunite them. There is no integrating force among the Hindus to counteract the disintegration caused by caste. While among the non-Hindus there are plenty of these “organic filaments” which bind them together. — Ambedkar, B R, Annihilation of Caste_ The Annotated…, 935