They really were just your "generic" conventional bike back then, that wasn't typically specialized for anything other than the possibility of being really ornate. The term most likely came from their use on beaches, when they by large fell out of favor everywhere else by the general populus(like real SUVs), thus were had fairly cheap by bike rental stands on beaches to ride on the boardwalks as a simple easy to use, slow, low maintainance bike. Something to cruise on the beach. The only other place they seem to be popular by numbers is in the hood. Imagine the white flight if they were called ghetto cruisers, lmao.