i think its because your worried about collecting dust on your head ie being left on the top shelf?.
Seriously all jokes aside, its quite common that alot more people are choosing the single {good} life these days, i believe that eventually we all have a reality check and look in the mirror and say what do i want out of life ie children, being married etc etc, there is no law to say that because all your friends have settled down you should.
Only you know what you really want out of life and if its time {if thats what you want} to settle down, i'm sure your make the right decision be it leading a single life or being in a relationship, in the mean time enjoy life to the full.