You can book two back to back tickets. I did it back in Feb on UA. CLT-ORD-LAX and LAX-HNL
which combined was $500 (including two $50 off coupon used for each ticket). Had i Just booked CLT-HNL (not knowing where they stop, but that doesnt matter) It woudl have been near $700 and I could only use one $50 off coupon. It is legal to do this. I belieev what you were talking about was booking CLT-ORD-LAX but then getting off in ORD. That's a no-no!