Really it’s just a misunderstanding of contract law. While it’s getting less common, because of esignatures growing in popularity, wet ink signatures used to be required on some contracts. Which is really someone just physically making a mark on a physical piece of paper. Basically sovcits decided that “wet ink” applied to everything, which I can assure you is not the case.

Here’s some more actual info about wet ink signatures:

https://www.adobe.com/acrobat/business/resources/wet-signature.html