There are idiosyncrasies for every group of people, however one chooses to group them.
If you are a native St. Louisian, then you will invariably ask where one went to high school. We ask it innocently enough. Really, though, we are evaluating economic class. We are determining what neighborhood are you from and how big the house you grew up in was. We are trying to find out if you are in the same economic class.
Jews do something similar. We evaluate status. Are you a born Jew? Since it is simply and absolutely rude to ask, little tricks are employed. What is your maiden name? What is your mother's maiden name? What shul did your grandparents belong to? What is your mother's Hebrew name?
According to the Talmud, the souls of all converts were actually present at Mount Sinai when the Torah was given (Talmud - Shavuot 39a).
In another part of Talmud, it says "a convert who comes to convert..." The phrase begs the question--why does it say "a convert who comes to convert..."? Shouldn't it say "a gentile who comes to convert..."? The reason is because it is recognized that the convert already has a Jewish spark inside of him/her.
Abraham ben Abraham, a well-known 18th century convert, said "Individual members of those nations sought to accept [Torah at Mount Sinai]. Only the refusals of their peers prevented them from realizing their aspirations. The souls of these individuals appear in every generation as converts."
Converts hold a special place amongst the Jewish community but they are still regularly singled out as being different. The status evaluation is but one way that is accomplished. Next time you are curious, please take a moment to STOP (the mouth), DROP (the curiosity) and ROLL (on to the next subject). Your local convert will secretly thank you for not having to yet again go through the status song and dance.