I keep saying those things too. And among my closest friends I usually go beyond and keep trolling them with "if you accept Jesus in your heart the movie will be good", Or "I declare this burger to be delicious in the name of Jesus".

Old habits die hard. They also usually constitute cultural touchstones that others understand.

Sometimes in writing I use the ironic and quasi-dyslexic "dog" in place of god but if I did that in casual conversation or in mixed company, a lot of people would wonder what I'm talking about or if I'm just trying to be a dick, so ... when I think to, I tend to use neutral substitutes like "that's a relief" in place of "thank god". But I don't obsess about it. Pick your battles, and all that.

God speak permeats our vernacular. Its colloquial & familiar. I don't believe blasphemy is the sole property of & only available to believers.

I'm not an athiest, but I still use those terms as well. You are just so used to using them. When a religious person pisses me off I say "god bless you", but it's not a complement. It's designed to be blasphemic.

I'm still in the habit.