[mdanger]

I had figured they needed to be there in person to get past the fingerprint scanner.

Also, Bane's plan centers around presenting himself as a champion of the people -- I had figured he went in guns blazing for the psychological value of the thing (not to mention the possibility of drawing Wayne/Batman out of hiding). Exchange security just being compromised probably wouldn't be a big enough deal for most people (the police officer outside who makes the comment about his money being in his mattress certainly doesn't seem to care!)