It's true. Swinging is the kind of simple pleasure that loses all of it's fun when you're all alone.
Unfortunately, as you get older it gets harder to find someone who will swing with you.
On a completely unrelated note, swinging was always funnest with girls, because whenever you got syncronized, yu could say "We're married!" And they'd say "Eww!" and run away. At least that's what they always did to me.