Two more reasons: certain brands of theists may believe that they are doing you a favour by trying to convert you, since they might save you from Hell—a fate, literally, worse than death. On the other hand, transactional analysts point out that converting someone is reassuring to theists who have a sneaking suspicion that what they believe is a myth. I suspect that getting their agreement that a religious point of view makes sense is a milder, but potent, form of assurance.