I think you're correct, though it's rarely that simple. I got married, not because I wanted to lead a traditional life, or because I was pressured to get married, but simply because I met someone who loved me and I loved them back. I was emotionally starved, which was partially due to being gay and in the pre-internet era so I didn't have much chance to safely meet another gay guy near my own age, but there is no doubt in my mind that there was (and still is) genuine love between us. It's just that I'm attracted to guys....
The pressure doesn't have to be "a great deal" as you stated -- society puts an expectation on us that isn't great, but it's constant. I'm sincerely hoping that that is changing and that the number of same-sex attracted men (and women) who get married because "it's what's expected" is decreasing. Certainly, at least in Australia, homosexuality is more and more acceptable, though it's not "mainstream" yet. Two guys walking down the street holding hands still attracts attention, though most of the time it will be just stares. Some places are better than others.
As a related point, when I came out to my wife she desperately needed counselling to help her cope. We were very lucky in that we quickly found a counsellor who specialises in dealing with women who have found out that their husband is gay, and had been doing it for more than ten years. I am aware that there is at least one similar counsellor in Sydney (from a magazine article a couple of years ago). My wife told me that the counsellor got into this line when she initially counselled men with AIDS. She found out that a number of them were married, and asked who was counselling the wives....
My version of this is "Putting people into neat little boxes doesn't work, unless you use a chainsaw."