In her interview with dalton conley, susan crawford shared findings of her research with lower-class religious women. she was surprised to hear that while the women said religion was very important, they rarely attended services at churches, mosques, or temples. why was this the case

I believe the answer is:  the stigma of being poor, especially at moments like the collection of offerings

It is a very common practice in religious places to collect some sort of offerings from their followers to help sustaining the operation.
During this time, some people tend to feel they're being judged from the amount of offerings that they give to the places.
To avoid the stigma of being poor, many of them decided to do their religious activities from inside their home.