Once these ranks came to stay and became rigid, those who got better and higher ranks tried to maintain that through different ways. They will not accept food or drinks from the people not belonging to their own caste.
Accordingly the will avoid dining and mixing with them. They will not like to have any matrimonial alliances with them. They then tried to have their own separate custom which distinguished them from the others and in their own way they tied to establish that they had better customs and status.
Caste ranking of course exits but in our times due to urbanisation and industrialisation on the one hand and popularization on the other, rank rigidity is not very much observed. Those belonging to lower castes, have managed to becomes economically and politically powerful and are being treated superior than the poor holding superior caste rank.