From the ancient time of Kings and Emperors, they dripped wax onto their royal decrees and seal it off by impressing the mark on their signet rings, declaring its clear authority of the scroll. Fast forward to today, this process has been modernised, "Kings" and "Royal Stewards" of a company are still doing the same by sinking their rubber stamp into an inkpad (or the self inking type) and marking it onto all of their documents. All these decrees of invoices, quotations , contracts, vouchers are governed by it. Or does it?
Let us just stop to think about it for awhile. So does having an "official" stamp on a piece of paper really means that it belongs to the company when anyone can easily duplicate it at a shop. What makes this worse is that they don't check whether do you really belong to the company that you are making it for. This means that absolutely anyone could "authorise" companies on your behalf. We shudder at that thought of it. Yes, we could sue them but how could we really prove against it? Why, then, are we still doing it? Inluding all the major corporations around the world are still practicing it. No one stopped to realised this scary flaw or maybe it's because no one bothers to try to make a change.
Moving on to signatures. It is even legal binding. But seriously, unless you are a graphologist (a handwriting expert) or works in a bank (which they scrutinize your signatures because it is part of their job) , who can really tell the difference. And from the other perspective, as a person looking at it, do you really care or remember what is legit or not? Take a teacher for example, can he really remember or bother to check all of the parent's signatures? Some signatures are so simple that even a child could copy it easily. Again, nobody bothers and we just slap a law to it and wait for someone to sue you, but can it be proven that it isn't yours.
Allow me to share a personal testimonial of an EPIC failure of the use of signatures. The iPad that i ordered from the online Apple Store was actually delivered, by a world renowed courier brand, to a wrong address. He actually delivered it to a private apartment block next to my office building and simply asked the security guard whether there was an Alvin in the block and of course, there will be, as it is such a common name! Then, this courier actually allowed the security guard to sign for it! Of course, the courier company will simply send any scrawls on a tiny piece of receipt paper back to its client and I know that , Apple or that courier company does not have any copy of my signature to compare against. But really, do you think anyone would actually check? After biting off a couple of heads, I finally tracked down the delivery man and gave him a piece of my mind! (Pardon this short rant)
So what is the cause of it? Paper. The biggest culprit for the invention of the rubber stamp and signatures. This is because these are the only ways that we can "authorise" or "validate" our identity on it. In this day and digital age, shouldn't we start saving trees and move away from all the limitations of paper? There are many modern methods that better protects your identity, don't you agree? With technology now that truly use what is unique and isn't easily copied, like ways of scanning fingerprint, facial recognition and even your iris. If you are not a fan of such body invasions, there are also simpler methods using your mobile phones like NFC, Bluetooth, D-Stamp, Beacons, IoT and yes, even with your phone , it has an unique identity. All of the above could be tracked easily with multiple data streams that better proves your identity.
This is why I am proud of bringing about a change to this ancient problem with a modern twist. The D-Stamp uses a unique digital signature in a physical stamp that can never be copied even if you break it apart. Here is a scenario of how the D-Stamp can solve the courier's problem when Companies use it in place of the conventional rubber one. When there is a delivery, the recipient can stamp on the delivery man's mobile device. With that action, the courier company and the sender can immediately get an authenticated notification while recording critical data like transaction time, delivery man's ID, client's ID, recipient ID and parcel details. We have also similar use cases on eVouchers for retailers as well! 
I'm not saying that it has a perfect security, but hell, they are definitely waaaaay better than a rubber stamp and "a scribble" on a piece of paper, don't you agree?