The worst thing about those is that the people who leave them smugly think they're doing a good thing. They're "spreading the word of god" and think they're helping more people to make it to heaven. But there's so many things wrong with that thinking, including:

• A non religious person getting one of those is just going to be pissed and think less of religious people.
• The person leaving it doesn't know whether the server is religious or not - they might be preaching to the choir.
• They usually only leave the fake bill. It would be more tolerable if they left an actual tip with the fake bill on top, but they're usually stiffing the server.
• In reality it seems like a way to skip tipping without looking like it until they're out of the building. You know they don't do this anyplace where they go regularly, which means at some level they know it's shitty.