Things were simple when I was young. You had a piece of paper, and when you had a phone number you wanted to keep, you added it. Every now and again, you got fed up of the lack of structure on your piece of paper, and wrote it out again. With the advent of computers, things became even simpler, because the 'writing it out again' step could be skipped.
Now matters have become more complex again. My phone has decided the time of passivity is past and is actively going out and collecting information on my behalf. I've got phone numbers of barely remembered school friends, birthdays of children where I didn't know the parents had got together and addresses which people will have moved on from before I would expect to see people again.
I'm not sure that I dislike it, perce. It does mean that I'm likely to get the information that I need, and saves me the effort of having to curate my own list. But I do miss the control - the certainty of knowing that the information I want has carefully been written down somewhere. That my records have permanence, and won't randomly be deleted when my phone decides that something it found online is better.