Do you know your spouse’s or best friend’s cell number without looking it up?
Remember that in ancient Greece when more and more things were beginning to be written down instead of memorize, there were philosophers who feared that men would lose the ability to reason and debate well because they no longer trained their minds with memorization. After all, what was the point if it was all written down and they could reference it?
And even still, if they did write it down, no punctuation or spaces were used. Language devices, pauses, phrasing, were meant to be discovered by the reader, not spoon-fed to them with word spaces, commas, periods, capitals and the like. Such devices, when they were gradually added, were considered by some to be an unnecessary crutch whose use would cripple youths’ minds.
So you see, it’s actually quite natural that I shouldn’t be able to recall but a handful of phone numbers today (even though I still remember my own and my best friend’s phone numbers from the mid-80’s). Yes, my children’s minds will not work as well as mine in some ways, and will not work the same in many ways, but that is how progress works. It changes us as we invent it. Some of those changes are for the better (we all have the ability to be far more informed on politics worldwide than ever before, and we were able to crowdsource the search of satellite images for the Malasian jet), and some are harmful (increase in anti-social behavior, adhd, unable to memorize phone numbers, and loss of focus for studying long, difficult texts such as the Aenid). And there will always be philosophers who will bemoan the latter.