People who do what you describe, ytl, are using their religion as an excuse to get out of working.
Truthfully, at my hospital, if someone called out sick at the lasy minute every other Sunday, they'd be let go.
Again, I think the "keep holy the Sabbath" idea, which is really what we are discussing, doens't apply in general as much to people who are doing necessary work for society(providing healthcare, runninng public utilities such as the electric company, policemen, firemen...you get the idea...)as it does to people who are doing unnecessary activity.
Working as a nurse caring for the sick on a Sunday...a necessary activity. Catching the sale at the mall or, to use the OP's original premise for starting the thread, shopping for furniture...well, would you consider either of those activities "necessary" to society?
I think that's the difference to consider when one discusses "keeping holy the Sabbath".
As a lifelong Catholic and a nurse, I've worked all shifts on all days of the week. The Sundays I don't work, I try to lay a little "low", relax, reflect. It's kind of amazing what comes to mind if you have some down time.