Another interesting angle here:
Yesterday, I drove into Hollywood to meet my sister for her birthday. We went out to breakfast at a new downtown diner, and went shopping afterwards.
While there, we spoke about this issue. (Strange, because she's not a believer.) I was reminded of my aunt, who lives in South-Central LA, not too far from where we ate. It's a gloriously integrated neighborhood, with blacks, asians, latinos, and white folks living on the same block, block after block for miles around. On the main streets, they have taco stands, burger joints, Jewish delis, etc. side by side in a peaceful setting.
If you drive past a park in the neighborhood, you'll see kids of all races playing basketball and soccer, and the little ones in the sandbox getting along just fine. Looks like a good situation.
But take a second look at Jefferson Blvd. or Crenshaw, and the churches are a different story. There's a church with the name "african" in the name, another called "la luz de salvacion," or something like that, and another with asian writing (Chinese?) with no English translation.
Melting pot neighborhood. My aunt has been there since the 1970's, and it has always been this way (except there a few less whites in the area now.) Everyone gets along just fine.
Except in church.
No one would have to drive or walk very far to worship in a mixed setting. Everyone already knows everyone, so they wouldn't end up in a room full of strangers. They simply choose not to. So there goes the lame excuse "we worship where we live."