What you are missing is that any H1B willing to work as a contractor by definition works for an intermediary. These intermediaries actually operate in a grey area of the H1B immigration law, take a percentage cut off the contractor's pay and therefore, the only H1Bs who work for them are those who can't find a job with a real software company. If you are lucky you may find someone who just lost a job with a real company and was forced to work for an intermediary.

My advice to you is to only interview H1Bs who have worked for other software (non-outsourcing) companies you have heard of before. If even those are hard to find, interview only those who have worked for top outsourcing firms say Wipro, Infosys and TCS.