Here's an example of where PGP is used.

A couple months ago RoboSats added it to provide auditable encrypted messages.

Easy PGP Encryption https://learn.robosats.com/docs/pgp-encryption

Prior to this, ... there was a weakness with RoboSats as there was no way to provde what was discussed in the chat -- specifically the payment instructions from the seller to buyer. So a seller could dispute that no (fiat) payment was made. But let's say a dishonest buyer purposely sent payment to some bank and account that did not match what the seller requested. In the dispute, the dishonest buyer would fabricate the chat message to indicate the seller did indeed request that bank and acct number. How could the dispute be resolved? Which side was lying?

So with PGP signing messages, that risk (of faking the content of chat messages) goes away.