I have to work today and so does my DH. I think it's a money thing with my employer, they don't want to pay everyone for another holiday while we aren't working and generating revenue. They are fairly generous over the course of the year though so I'm not complaining. DH works in health care and so his employer never closes but they don't count Good Friday or Easter as a holidays anyway.
I don't think Christian owners really have much to do with it, I have a friend who works at a Christian school and they aren't off today.