I think the chrome merely protects the steel at the cones and front part of the barrel from wear by the steel shot. I don't think tightly choked chrome plated barrels would be any safer than non plated for steel shot. (note that most modern choke tubes say "not for steel" on the full choke tubes).
Chrome lining is usually a cheaper method of getting a smooth polished surface on the inside of the barrel. The chrome will self level to a smooth finish without additional operations, this saves additional polishing that would be required to polish the bores smooth in an unplated barrel.