A couple of possible reasons for changing from 'steamboatin' to 'river cruising'
without regard to dieselization foreboding: !) if they are lumping all their boats into one promotional deal, not all are steamboats and therefore steamboatin' doesn't work for those non-steamboats. They probably want one ditty for all. 2) Steamboatin' was a copyrighted term. Now whichever DQ regime copyrighted it, I don't remember. I don't know if the copyright stands if the entity which owns it is no more....