its not a matter of Halachah.
its a matter of following the manners of the Tzibur
they are makpid on this at Telshe Yeshiva
its just a sign, thats all, a statement.
like the couple who finally divorced because the husband kept asking his wife to close the toothpaste tube and she kept leaving it uncovered. he felt she didnt care what he had to say about things, that she didnt respect him, of course it was silly but every time he saw the open tube his anger and hatred of his wife welled up.
its not the bobby pin, its what the bochur means by wearing it