I've always wondered about this myself as I'm not familiar with dispute resolution for something like this. However, it seems like part of the resolution if an establishment has cameras it seems like they can pull up the frames for the time displayed on the receipt, and present that as evidence that you signed (scribbling shouldn't matter). If it wasn't you in the video then it could be fraud or a friend/relative using your card.

I've only seen investigations for online orders, digital purchases, etc. and not for a restaurant-type setting so it would be interesting to know if video can be used.

If a business claims to collect signatures but doesn't save the receipts/signatures, they'll find it harder or impossible to contest chargebacks. So if nothing else it makes it slightly less likely that banks will eat the charge.