I am someone who was not given a caste-based last name because my parents were influenced by a regional movement against caste. (I didn't even have a last name to begin with but eventually added a non caste-based one to avoid visa issues.) Whenever I traveled by train and chatted up with a co-passenger, almost surely they would ask my name and would never be satisfied with just knowing my first name. They would get visibly confused when I would tell them I didn't have a last name.
Edit: Curiously, based on the last name of the person (Soundarajan) whose talk got cancelled, I would actually have guessed that they were upper caste (Brahmin - the highest).