My understanding is that banks are incredibly easy to rob, it sounds like you can legitimately just walk up with a note that says "I'm robbing you, give me money" and they'll do it. I think you'd have to know to look for the trick money they have, like the ones with dye packs or are marked or whatever, but besides that, I dunno-- it sounds like every time I hear of a bank robber, they get caught on the third bank job, or the fifth, or whatever.

My only information comes from being really interested in this and reading any article I can get my hands on, but law enforcement and security people sure make it sound like if you don't get greedy, don't actually hurt anyone, use a little common sense and walk away after the first one, there's an extremely high chance you'll get away with whatever you get. Go somewhere a few states over, use fake plates, and all the police will have is "Random person we've never seen wearing a hoodie" and won't do much about it. The banks are insured and directed to comply for safety, so they don't care too much.

(please don't take this as an endorsement to rob a bank, and remember this is all just a layman's understanding)