There's a distrust of programmers because many programmers are not at your skill level. You don't seem to have problems with finding employment. Perhaps open-source contributions don't matter to people of your caliber. But you need to realize that it's not HR or management asking to see your code -- it's your peers.
We need as many metrics as we can to find out who's good and who says they're good. Looking at code and examples of work is exactly how you do that. You can argue all you want, and it may not be fair. Neither is "You have to have a 3.5 GPA to get a job here."