At least in EU that would be a legal requirement (Payment Services Directive rules that limit liability for unauthorised transactions), not graciousness/PR of t

At least in EU that would be a legal requirement (Payment Services Directive rules that limit liability for unauthorised transactions), not graciousness/PR of the bank. FDIC insurance (and its equivalent in other countries) is something completely unrelated - it's for cases when the bank is unable to pay you because it goes bankrupt for some reason (which may include massive fraud done to the bank or by the bank), it's not for cases when your money gets lost in some other way.