If you are a true follower a set of religious or spiritual practices/beliefs, I completely understand, but if you don't, what's your reason?
Are you bad at socializing with others? Do you feel like one-on-one creates a stronger bond?
Is it too much work to juggle people? Is it too much work to find a good partner in the first place?
Are you unable to attract anyone of higher quality? Do you want your story to be like Disney? Do you have no idea, and have I given you incentive to explore your options?
Do you just want new experiences but you feel powerful because you have complete commitment from someone? What is it? Do you just not have any self-control when you see someone hot? Do you not think it's morally wrong or?