So you're saying the signature itself is irrelevant? It's just an elaborate checkbox? The question then is how do you prove I was the guy who checked the box?
A signature is somewhat harder to take them and checking a checkbox and can be somewhat more easily traced back to the signatory, so it’s probably somewhat better than a checkbox.
You're free to counter and say it's a forgery just as you would be to counter and say someone stole your private key. But the point of a signature in particular is that it's supposed to signal considered intent rather than mindlessly checking a box or being rushed and saying "sure sure whatever."
We pop up dialogs to ask users for confirmation before doing dangerous actions. What's wrong with the paper equivalent?