Why am I single?

No seriously, People like me, sometimes talk with me till it's pretty late. Talk with everything about me, call me pretty much daily. Sometimes I can't understand why I'm single. I nice around people, help them, always having an open ear. People told me before what a "good friend" I am, but I think it's kinda sad. No interessted in you, all people around you see you as a "friend" nothing more. I mean I'm not that old but I'm slowly walking into my late 20s and I feel strange about it, specially having so many couples around me.