Once upon a time in a faraway land the process of authenticating a document was labor intensive. Those who generated documents were few, and communication slow, so a document which arrived at your doorstep had to be examined with due suspicion: was it signed in the proper format, was it sealed with a seal which bore the imprint of a signet ring, or for monarchs perhaps the great seal. All of this reflected a prudent lack of trust; people were loosely connected and individual transactions were rare but very important so fraud was tempting.
Even 55 years ago, a rite of passage was determining what my legal signature would be: William David Harshaw, William D., W. D., W. David, or Bill. And I took a little care in practicing the signature, before beginning to sign checks and college applications and such. Early on I was proud of my signature and theoretically the bank could examine the signatures on my checks to determine whether or not they were forged.
But today you watch people at the checkout counter using a credit card in the card machine--they stick in the numbers or slide the card, then scribble a signature, very often in my observation just a squiggle which is almost a straight line. Even when you go to the bank these days, signing some bank documents, you use the same technology. From my limited experience it's impossible to use the technology to sign legibly. I'm sure the variations in signatures from one time to the next are much greater than when signing with pen on paper, so the likelihood of an expert being able to authenticate such a signature is much lower than in the past. But that's okay, because we do so many transactions which don't really matter much. The effect on society is to make us less suspicious and more trusting.