I think a lot of people who go into relationships without much feeling are just people who feel like they need to be in a relationship in order to be happy, and so will convince themselves that they are in love to validate their relationship when they actually aren't. I don't think being in a relationship is a societal obligation nowadays; in the past there would have been pressure to find someone to marry at a young age but that pressure doesn't exist for most of us now.
As for going into a relationship with someone you don't love...I don't think you have to be in love with someone at the very start of a relationship. I know that when I met my boyfriend, I was attracted to him and I knew I liked him an awful lot and wanted to get to know him better, but love didn't cross my mind until a few months later when I realised that our relationship had shifted from one of intense like to one of intense love. Although I suppose I knew I did feel something for him romantically when we started going out, it wasn't love at the time; love took time to develop. I think you have to know someone quite well to be able to say you love them or are in love with them, and if you don't feel that after a certain amount of time, it's probably just not meant to be.