Because homosexuality is a lifestyle and way of living. Other sins are a character flaw, the idea of being delivered from stealing, lying, murder etc is more tangible then telling someone their life is a sin. It is very sensitive and takes one to truly be humble enough to accept this fact especially since the New Testament has a heavy emphasis on love and homosexuality is essentially love in the “wrong way”. That’s why we have Christians now who accept it under the basis that God loves all.