The senior staff at most unions are people who have thought about physical labor and the skilled workers who do production work. Programming as a profession is still relatively new career path.
My first union tech job was in the medical industry and we had to jump in with the nurses to find representation. It was good enough but our jobs were dramatically different. And our pay and benefits were much better than the nursing staff. The union had a hard time being able to deal with both of our different problems.