It's the complex humans have with the unattainable. An oreo cookie may cross your mind, but as soon as you're told to stay out the box you device a plan to get to the top shelf as soon as dad falls asleep. Some PEOPLE (not just gay, straight as well) get their thrills from manipulating people. Sometimes it's just the sick mind game that gets them off, sometimes they have deep insecurities and, if they can turn that "straight" guy into dicksucker, they feel that they're desirable and have value. That, and sometimes bored, makes people go after things they can't have. And we ALL know people who get off on failure. I'm sure that although every story on this site suggests success, there are hundreds of gay men who FAIL to convert the straight guy, alienate a good friend in the process, or end up hurt, crying, and blogging about being rejected. Some people WANT to be rejected, it gives them a chance to be the victim. They're more afraid of success and reality, so they pursue what's unrealistic and sure to fail so that they can say they tried and validate their attention-seeking feelings of inadequecy. "Poor me! I couldn't convert him! Woe is me, show me love, give me support, tell me I'm desirable. I must not be cuz I couldn't get that married pastor to leave his wife and kids and marry me in California!" or, in the earlier case "Guess what I did last night! My straight friend came over. He only likes girls but I totally got him to let me feel his cock. I'm so sexy I convert straight guys!" Some people don't understand that they're being manipulated themselves by straight guys who like the attention of gay men and are simply open-minded in their behavior, but have no desire whatsoever to be with a gay person, relationsip-wise or even sexually. Many gay men think "If I can get him to grab my ass, he'll leave his girlfriend and whisk me away to happiness!" All in all, it's probably either being naive, needing validation, being self-victimizing, or the joy of breaking up happy homes.