The difference for me would be simply freedom of choice.
If I was single and choose to go with out sex thats my choice. And I have the option to change my mind at any time. I know that if I choose to have sex it would not be a problem to find a willing partner (beer googles if needed). But if I am married and the one person I am to have sex with is not interested that takes me into a area where the lack of sex is not my choice more of a forced issue. Which really changes the whole dynamics of the sitch.
In one case I choose to not have sex. In the other case someone else chooses that I do not have sex for me.
