The answer is very simple and that is because of the way we are raised - our society.
Just think about it, when you walk down your neighborhood in the US or any western country, how many people know you? and how many come to talk to you? (It's a little different when you're in college because everyone sees everybody almost everyday)
Now imagine the same scenario in Nepal. You almost know half the people you see when you're walking in your 'tole'. You have to give the customary 'tyaha samma jana lako' or 'tyeha samma gayera auchu' and noone asks you back where you're going but will acknowledge you.
The difference is individualistic society versus communal society. In our society community matters. This could be a side effect of failures after failures of any government that comes into power. But essentially in Nepal people have learned to co-exist among themselves with some kind of human bond with people in their neighborhoods.
I don't think there is anything wrong with that. In fact when we go back to Nepal, it's nice that a lot of people acknowledge you when you walk by. You see many people that you know. That's what makes it fun to go back to Nepal besides of course the the time with family. Even with extended family we share stronger bonds than people do in western countries. Even the friendship we have in Nepal is stronger than the ones you find in the western countries.
With all that closeness and human bonds it is likely that one is more curious about others in Nepal. In addition, another factor increases this excessive curiosity and that is the division of classes. We have grown up with caste system and we love to classify people according to thier status in life. So we're curious about their social status and that means personal status in life. Hence all personal questions.
If you don't understand why Nepalese people are Nosy, you might be losing the essense of being 'a Nepali'.
After you've lived in the west, your curiosity about other's personal status might go down because you learn to adjust in the society you are in currently. So chances are you won't be stopped to ask your personal history/status by someone who's been in the west since they were young like if they come to the US before their early 20's for college. If someone comes from Nepal after let's say late 20s or early 30s then it's hard for them to adjust to the individualistic ways of the west and they are still found once in a while in busses, trains, nepali parties, asking you these questions.
God bless them too. and may god bless you too. Happy Dashain!
