Was more thinking the backpack variety vs car variety, and looks like the folding kayaks are there ease of storage rather thank transportability.
They were originally developed to travel by train in pre-war Germany, and are transportable by plane, helicopter, submarine etc.
I used to know a sea kayaker in Ireland who arrived at meets with a Feathercraft K-light kayak in his backpack having taken public transport, which weighed 15kg. Their replacement is the Kurrent which weighs 14kg and might be manageable.
I have taken my Klepper Aerius 1 kayak on a train and portaged it from the port station to the jetty on its compact trolley. I would not try to backpack with it, though.