neighbors

I always wonder why neighbors never talk/meet anymore. I live in a small neighborhood where the houses are about 20 feet away from each other. Growing up there were(and still are because they are almost all still here) 6 houses around our house, where all the kids played with each other no matter the age, and all of the parents were friends. They did stuff together, etc...fast forward 15 years. My next door neighbor moved out, and about 2 years ago another couple moved in. They are lovely people(we met them 2 or 3 times) but they have no desire to want to become friends, or even talk through the fence to say hi when we are both in the backyard. It we(my parents or i) are leaving and they are outside, we always make an effort to wave, say hi, etc...and they always wave back, but they look like they just don't want to get to know anyone in the neighborhood. We are all nice people here, no gangsters or drug dealers or anything like that. Most of the people around my house are my parents age with adult children. So why don't they open up? And its not just here its happening. More and more people are keeping to themselves and not sharing. Now i'm not saying i want them to become instant friends with us or anyone else, but just to be friendly. People put themselves on guard with other people now, and that just isn't cool. I am a very openly friendly person, maybe too much, but i always make an effort. I guess I am rambling here, but do you the reader know what i am trying to say? I hope so, because its 2am on christmas, and due to my nephew we have been up since the crack of dawn. Happy day after christmas, and remember, only 365 more shopping days til next year.