They do not think that their health, or their life, is worth protecting. Low self-esteem is very common in the Gay community, and is often related to the way that society treats Gay men. Some men are willing to take their chances, and the consequences. Some men who are already HIV positive think that they no longer need to use condoms, and are unaware of the health consequences of HIV reinfection and the risks of other STDs . Some men are in denial that they will ever get infected.
Some men simply enjoy barebacking better, and think that barebacking is worth the risk.
Some men simply hate using condoms. Men complain about condoms giving them less sensation, and they also complain that they are more likely to lose their erections while using condoms. Some men also find putting on condoms to be a hassle. A common complaint is that condoms interfere with sex play. When a person is drunk or high on drugs, they are more likely to bareback.