Just seems like a waste of money to me. Not sure what the D&D DMG provides that the other two don't (or at least T&T for A5e; I don't have TotV's DM book yet.
I don't want to badger any player, but part of the class narrative of the class the player chose is that they receive their power through an agreement with a patron. That patron IMO needs to matter to the campaign.
One: sometimes they do. Depends on the god. Certainly other members of the faith might take a more active role.
Two: warlocks patrons (mostly) seem to have a more intimate relationship with their warlocks.
Whether the PC cares or not, I still believe the answers to those questions should matter in the campaign if the player chooses to play a character who gets their power from someone else.
Funny how all those options mean the patron isn't important in actual play at the table and functionally mean they have no effect on the PC other than being the vague source of their super powers.
No thanks, personally.