Contrary to what some might believe, many airlines, in their operations specifications (which are issued by the regulatory authority, and not just the FAA, either) specifically mandate certain requirements, and those requirements often specify what type of pilot headset shall be used in normal line service, and which ones are disapproved.
Those pilot headsets which do not carry a TSO specification are many times excluded, IE; cannot be used.
I know of two airlines that had this requirement in their ops specs, and pilots found using non-approved headsets were promptly removed from flight status.
However, it would seem that a few pilots like to demonstrate their 'individuality' and ignore the stated requirements.
Too bad for them.