But bravery isn't the only trait of a Gryffindor. And there's different kinds of bravery. Calling people on the phone can take bravery, talking to strangers. Asking someone out on a date or to agreeing to dance... And they're also rather stubborn, they're very firm in what they believe is right and wrong and don't tend to change their views very easily.
You have to keep in mind that the traits of the houses are much deeper than people realize.