Yes atheist does refer to “no God”, but its a lack of being convinced that the supernatural is part of reality, not a positive statement that there actually is no supernatural. Just like if I fail to convince you that I bought a puppy yesterday. You don’t actually know that just based on the evidence and argument I put forth in the conversation, but you were not convinced/believe that I did purchase a puppy yesterday. The default position of any claim about reality is to not believe it until you are presented with enough evidence to accept the claim to be true.
Yes there are “atheist churches” being setup but they are not preaching “Atheism” as I understand it. The cause behind this process is that the people that have come out and told people they don’t believe in the supernatural, aka are an atheist, are then kicked out of the family and their churches. They have now lost their social support structure that was supposed to never leave them. Now there is a vacuum in their world where they are still wanting that social community and family. So these churches are popping up to fill that. They are discussing all the things that are important to people in church, minus the attachment to the supernatural. So they talk about how to be better brothers, sisters, mothers, fathers, husbands, wives to each other; discuss the stresses of living the good life as a community and as an individual; implementing social works within their communities like food banks, libraries, etc. All without a need to reference the supernatural as a reason to do better. These churches would not be there if their family and church did not kick them out and ostracize them.
People brought up in a specific cultural tradition that teaches them what practices to do for emotional release during highly emotional events. If you’re really stressed about and feel helpless about something and your culture taught you to pray, well just the exercise of prayer will reduce your stress level and help calm you down about the situation, even if you believe you are not actually communicating to a deity. We all do this, that’s why we punch the ground out of frustration, rend our cloths at terrible news, kiss photos, etc. We all need rituals. Its just easier to use the rituals we were already taught from childhood than make up our own.