This is strange to me. It could be seen as an aversion to heavy-duty committment. This way I can have pretty serious relationships, which is certainly where I lean, with a lot of that Relationship Pressure removed from the picture. Of course, I haven't been in a long-lasting r'ship with a non-married person, so I may well be imagining a Relationship Pressure that isn't there? Who knows.
I have no complaints about my relationship history, nor my relationship present, or, at least, very few. One of my favorite things about being poly is that I get all the benefits of being in a relationship, and all the benefits of being single. That's not always been the case, certainly, but I'm in this great place where I have a steady relationship in which I feel totally secure, and I get regular dates, and I also have the time and space to be doing my own thing a lot of the time, too.
Although I always say I think I could be as happy being monogamous as being poly, it's currently really hard for me to imagine that I'd be as content/fulfilled. And that's just as well, since all my current involvements/interests are married people living in the suburbs.