The statement should be that the media doesn't report on it anymore. Bank robbery hysteria was a fad from the 70s.
Read your local newspaper or the police department crime blotter; bank robberies still happen. The take is diminishing and the risks increasing though.
ROI is better on ATM theft. Clever thieves can subvert them with USB malware through hidden access panels. They still run crap like Windows CE (or whatever the Embedded version was).
Is there evidence of this? Anytime someone mentions declining crime rates its always with "well, they clearly don't report it!"