

The point of the signature isn’t the mark, but that the affirmation on the document can reasonably be tied to you. For most of history, it has been tied to a certain mark, whether it be a signed name, a stamp or embossed seal, or even a drawing. That system generally breaks down in the digital age.
A low hanging fruit that is seen to work is having the mark of approval get tied to an account under the control of the signee. It isn’t so much that you made the mark but that it is tied to an email address you control. So even if you don’t sign it with an actual signature, it still gets tied to you.



For a physical only document, the mark is something relatively difficult for others to perform. Even then, signatures by themselves usually only carry a certain amount of weight by themselves; either the risk of borne by the other party or additional measures are taken like requiring witnesses including notaries.
To answer the next question you’ll probably ask, it is considered to be far more trivial for someone to apply someone else’s mark digitally than it is in person. Anyone with a pdf editor can apply someone else’s signature to a document without their knowledge.