This came up in a thread over on The Bump - funeral thank you notes. Apparently, some people say you have to send TYs to everyone who comes to a funeral. Is this actually a thing? I tend to think TYs fall the same way as weddings or anything else - yes, you should send TYs to people who go above and beyond in giving a gift, making a meal or providing a service, but you don't send them to people who just show up.
I tried to google and find if Miss Manners had addressed this anywhere, but I couldn't find anything.