If I gave out my phone number to everyone that asked for it, the company I work for would be getting free use of my cell phone all he time. I don't have a long list of friends, so I don't need to give out my number much at all. Generally speaking. My phone is there for me and my Wife, not many other people. It ring only when it's necessary even from my wife.
Like said above, My phone rarely gets picked up unless I am expecting a call, and I have the phone on me or near me 24/7.
In these tech times. Your phone is not just your phone. It's your camera, your computer, your calculator, your resource center, daytimer and so much more it becomes pretty important to have it after you get used to having one.