Because in the end most people just let you down? 
I moved to a new area six months ago. I have met lots of people and some may become frienships. However I'm not sure I actually want that. Prehaps I'm better off just being with my DH and Dcs.
A couple of months ago I went 'home' to visit my friends, out of my group of 6 friends, only 2 turned up to see me.
1 lied (good old facebook) about why they didn't come, one contacted me to make arrangements which i replied to, then nothing, others just didn't bother. 