Like you guys said I never took a conscious decision about it, Just doing my PhD somewhere different to my undergrad degree I had to make new friends both in the department and out of it, trouble is that alot of these have now left and those that haven't are busy in their final year, the time I would have spent with them has just been taken over by work.
As an undergrad I used to got out all the time but now all the rushing about of societies and clubs I don't have time for anymore