There are tens of millions of people [1] who work on Sundays - something that has occurred as we moved into a 'modern urban economy'. I'm not convinced that moving it to a weekend would make any noticeable difference in the numbers. The weekend is no longer 'special' except mostly for white collar professionals.

[1] I couldn't find any actual numbers so I was just looking up retail and restaurant industry jobs on the BLS website, but WiseGeek claims (without a reference) that the BLS says 35% of Americans work weekends.