The literal difference is that most IT employees are "Exempt" and employees in many other fields (construction, retail, etc.) are "Nonexempt" under the classification by the Fair Labor Standards Act. A FAQ from the Depart of Labor on the FLSA:
http://www.dol.gov/whd/regs/compliance/hrg.htm
Here's a post from the Whitehouse from last March, where they discuss some of the overtime issues for white collar work with the FLSA as it stands:
http://www.whitehouse.gov/the-press-office/2014/03/13/fact-s...
To continue the hijack, this is largely the case because IT employees have been loathe to unionize or organize in any way. For many reasons, those in all parts of the computer industry have avoided organizing their efforts which manifests with a pretty unfair power balance between employees and employers.
