"Hey."
"Hallo."
"How are you?"
"Can I help you?"
THEORY...
Like travelers in underground or customers in fast food establishment. People only notice each other but they not interact by any means.
If something happens, something extraordinary - then people start to interact. They comment, they change opinions, they arguing. Some happenings can be a good reason even for a new relationship.
But what if you have such good reason with you. If your appearance is an happening itself. If logo on your apparel says something to people around you. What if your t-shirt logo happens to be so intriguing that people involuntarily start to comment.
The ice is broken.