I have found that many LGBT couples are willing to share their bed. I have a few ideas as to why "all of a sudden" this is normal and visible:
1) LGBT people are rejecting traditional marriage values because of its religious implications
2) Society as a whole generally accepts simultaneous multiple partners
3) LGBT people are naturally noncommittal
4) It had been bred into us
My personal opinion is the last. Its been bred into us, we have been forced to embrace such behavior.
Homosexuality had to be hidden for several hundred years. Open relationships for LGBT people have been largely impossible. As a result, "relationships" had to be discreet and quick. Maintaining 'straight' relationships with the same people they were with the night before. It was a silent agreement to keep life rushing forward, your feelings had to be suppressed.
Most gay men I know like the idea of a monogamous relationship but are quick to admit they would need the room to have alternative sexual options to remain happily married or in a relationship. Strangely enough. Which begs the question, why attempt to settle down at all?
Not all LGBT people are like this either. I find it neither bad nor necessarily good. It just is. I fit into the former category. My ideal relationship is to be the "plus one" for an established couple. Where I am dedicated to them and them to me. But that's just me.
Not everyone wants a 'poly' relationship. My only bit of second thought is reconciling my relationship with Christianity. Because I am, and proudly so, a Christian. Whether other Christians like it or not, for that matter, whether other LGBT like it or not. The Bible says there is no marriage in Heaven. Furthermore, if marriage is the union of two souls, why cannot it not be three? Surely if you knot two, you can knit three.
I suppose the question shouldn't be if a habit was bred into us or forced onto us. The question should be, should we try and change it? Is it a bad thing? To be honest, I don't know that we should.