I have the opposite problem to most people, of having too many friends. And the number is ever-growing. Wherever I go - job, hobby, school - I pick up more friends. It's wonderful in that I am never lonely and I feel very loved. It is difficult though too because I sometimes feel overwhelmed and that I am not able to be a good friend myself. I have so many invitations, emails, texts etc that I can't keep up. I adore the majority of my friends - but it is quite difficult to extricate myself from a few friendships I have that are draining.
I've been thinking recently about why I am this way...and I believe it is down to 1) listening carefully to what people have to say, 2) being happy and calm, it is just my nature, I am quiet but I am always looking for something to laugh about. I like to crack little jokes and I appreciate humor in every situation, 3) being un-judgmental and kind.
Anyway i'm not sure what my point really is, except that you CAN make friends as you get older! It is not all doom and gloom :)