Kathy and Tommy's unconventional romance is because they are never exposed to love that is deemed normal by society. The guardians don't show love, the donors don't have any parents figures to receive love. The only love they ever truly explore is sexual love and what is seen briefly on the television, no one has ever told Kathy that they love her. Therefore, she wouldn't tell Tommy. Donors, especially Kathy, don't realise that love is both spiritual and physical.Which is why they would appear cold, distancing themselves from the reader.