The shoes can harden and glaze over with age. So I'd replace them myself with decent quality replacements (Delphi are good).
The cables are very long lasting, so it's unlikely to be those.
It's most likely to be the rear shoe assembly is corroded and not working correctly, in combination with glazed shoes.
However before adjusting the rear brakes, make sure the handbrake compensator is backed right off, or correct shoe adjustment can't take place.