"I'm sorry you feel that way" is not an apology (expression of remorse), it's an expression of regret: "How unfortunate for you, but it's really nothing to do with me." And the implication is indeed that the speaker has done nothing to apologize for, so why be remorseful? If someone still feels owed an apology, then perhaps it is appropriate to say, "Well too bad Old Sock, but tough shit." When did we start owing people apologies just because they said we did?