Well marriage doesn't function in the way it used to in terms of deciding our fate but it's in our heads and it determines a lot of our actions. Like right now if you think about gay marriage - and they just started having the first gay marriages in New York - it shows what a potent idea marriage remains for people.
Christopher Reeve did such an amazing job that to give him some kind of accent or more bravado would have been wrong. Audiences wouldn't have responded to that either.