1. I’ve noticed that people in the South use first names much more commonly than in the North. I can think if a simple explanation for this – south indians either don’t have family names (tn, old mysore) or have unpronouncable/hardtoremember family names (andhra/kerala). so a south indian Siddharth Tata is likely to introduce himself as T. Siddharth whereas a north indian Siddharth Tata is likely to say S. Tata.
2. I’ve noticed in my extended family that concepts such as “aunty” and “uncle” made their entry only in my generation. I’ve never heard either of my parents using either of these words, or any of their Kannada synonyms. Everyone is addressed by their first name, irrespective of whether he is nephew/cousin/uncle/granduncle.
However, this firstname thing stops at the family level and doesn’t extend to work. People unrelated to you instinctively become Sir or Madam (this is in my parents’ generation. I don’t know how people in my grandparents’ generation addressed unrelated people). In fact, all of my mom’s male colleagues used to address her as Madam (or I should say may-dum).
I don’t have data to support it but it is possible that this Sir business has something to do with the British Raj, and wasn’t common in South India before that. I don’t know how far back the “ji” system in the North goes (i know it goes back at least as far as Gandhiji), but my general sense is that it is fairly ancient.
Ok – so – here is the hypothesis. We Indians are not hierarchical at the family level. Despite all talk of “don’t question your elders” and similar sundry stuff, I don’t think at the family level we are inherently hierarchical. However, go beyond the family and the caste system takes over and brings in a social hierarchy – which is why everyone outside the family becomes “sir”, etc.