Because I’m probably a sociopath. It’s tough for me to stay interested after a few months. I have never started a relationship with someone because I was genuinely interested in them. There was always a need I wanted fulfilled at the time and they fit the bill. It was either I wanted sex regularly, or not to go on vacation by myself or spend Christmas alone, but never because the girl and I had something in common or she was interesting. After a while the person would assume that that we were a couple and because I liked the sex or companionship I’d just let it ride out.