Men cheat because they are selfish and only care about their own pleasure. That's the reality of the situation, Dallas. It's a sad fact because it's true.
I'll tell you a little story:
There was once a gay man who "hung out" with another gay man for about a month and a half. They went out to dinner, watch movies, held hands, & hooked up several times -- and of course cuddled. After that month and a half of getting to know one another on a somewhat personal and intimate level, 1/2 of the gay pair, who we will refer to as BIGGEST ASSHOLE ON THE PLANET, lets the other one know, who we will call POOR WELL-DRESSED VICTIM, that he had some other gay guy, who we will call STUPID-ASS CRACK WHORE, suck his dick. To compensate STUPID-ASS CRACK WHORE for his service, BIGGEST ASSHOLE ON THE PLANET proceeds to masturbate him. POOR WELL-DRESSED VICTIM is distraught upon receiving such information from BIGGEST ASSHOLE ON THE PLANET because he thought this month and a half of hanging out was actually leading to something. He gets very, very upset at BIGGEST ASSHOLE ON THE PLANET (BAOTP) and refuses to ever talk to him again. BIGGEST ASSHOLE ON THE PLANET replies with, "I thought we were just hanging out. I didn't know something was going on with us. It was never official." POOR WELL-DRESSED VICTIM (PW-DV) is flabberghasted by the gaul of BAOTP. PW-DV is an idiot and a couple of months later forgives BAOTP after weeks of shameless apologies. PW-DV however becomes so paranoid that BAOTP will fuck up again that he could not help but worry everytime BAOTP is out somewhere else. PW-DV then breaks it off for the second time because he could not trust BAOTP. In short, BAOTP ruins PW-DV's ability to trust men.
There's the story kids. I hope you learn from PW-DV's mistakes.