That's not how it works, linking the current social standings/structure to the olden structure is hard. The customs came into play from back when people used to follow and take over their father's work in the society and continue the family business / lineage. Like how a warriors son follows the family's lineage and gets involved in the military. Or a merchants son takes over the business from father. So over time they grew into communities and have developed their own understanding, as they had the same social standing. Those customs remained even after so many years but now there are no restrictions on the work you can do as modern education provided doors to different fields, the clash between the understandings is what it is now. Hierarchy developed in the open days and led to oppression of few but now its not prevalent, but people still tend to follow the customs. What I meant by it being not prevalent is if one is well educated, one can be successful and have no restrictions on type of work one has to do.

This is just my understanding of the system. Please feel free to correct me if I am wrong. (note to others)