Most of mine, too. I don't think I've worn a real, cycling-specific jersey in eight or 10 years. Too much like putting on pads to play catch with your kids in the park.
As a side benefit, I think drivers are more courteous and give me more room when I'm wearing a t-shirt or something like that. We have a lot of testosterone-crazed wannabe cyclists here, and drivers react negatively to them. When they see somebody just pedaling along like they're out for a ride, they cut more slack.