One of Dawkins' theses is that many Christians just identify as such because "Christian" has historically meant "good" or "normal" in many communities. In these communities to introduce yourself as a Christian gets a slight nod and the conversation moves on but saying you are an atheist (or otherwise) makes it "a thing."
I remember growing up Catholic and hearing news that some friends admitted to being atheists. This had the same feel as hearing friends had admitted to being thieves, liars, or cheats. Lots of whispering, rumors, and altogether reprehensible behavior for such a stupid thing. It had less to do with disagreements about true, deep belief in an all powerful deity and more about saying "we are not part of the team" and being tarnished by admitting such.