I'm with Kim on this one. Some times it's an emphasizer & sometimes it's really a plea. There was a time when I'd hear some one say "God, ... " & I'd ask them if they really wanted God involved with whatever it was. Usually I got a blank stare because they had not realized they'd even said it. That's in vain to me. I think it's the thoughtless use that's the problem & I suspect the Muslims who say it all the time may be equally thoughtless.

I do occasionally hear someone say, "God willing, we will meet same time next year," or the like. It can be truly meant & maybe appear a bit sanctimonious, or just be a throw away line. I think our (US) culture is such that we feel uncomfortable hearing & using it. Whenever my aunt's mother-in-law talked about her mother it was, "My mother, God rest her soul, ..." That hit me oddly when I was 12.

Weird, we probably feel less uncomfortable with a vain "Oh, God" than a really meant "God willing"

There are a number of religious groups that will not swear oaths in court because there's a passage in the Bible where Jesus says not to swear by anything (heaven, Jerusalem), but to let your Yes & No be for real. How did our 'Christian' nations get so far from following this injunction that we actually have people swear by the Bible?