Skimming through RTT for this week, there were up to 10 freights daily that actually ran on the S&C, plus numerous unused paths. There are frequent workings from the Arcow quarry near Horton and from British Gypsum at Kirkby Thore. These flows would have to go by road if the line closed. Additionally there are through workings between Settle and Carlisle, which would otherwise need paths on the WCML or ECML.
Train information at Settle Jn all day on 09/04/2021. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk
IMO keeping HGVs out of the Yorkshire Dales National Park is adequate justification for the line to remain open, so the infrastructure savings from removing the scheduled passenger service would be modest.