Also because atheists are a lot like vegans. How do you know if someone’s a vegan? You probably have to be told, because you aren’t paying that much attention to what other people are eating.

A lot of religious people only notice atheists when they’re being annoying. If you’re a Christian who’s not annoying about it, it’s not like you’re asking people to do stuff when a Christian would be busy, you’re more likely to default to assuming they just go to a different church.

There’s also people who take being told when it’s relevant as a pushy annoyance