Interesting observation.  I've always wondered why certain people (or companies) won't work on Sunday, when the biblical Sabbath is on Saturday.  (That was changed by the Roman Catholics so that they weren't celebrating the same day as Jews.)  And what people do or not do on the so-called "holy day" has evolved by custom more than by religion.  If a person needs to work on Sunday, and if that person won't, then he need not apply for that job at that location.