To be honest,Mrs.Lag is just the same for the exact same reason.She has only ever driven on motorways a hand full of times and panics every time.Usually shes quite a confident driver but show her a motorway and she becomes a gibbering wreck!.
Exactly the same for my wife, and she freely admits it. She says it stems from having an old underpowered car when having first passed her test (didn't we all), and venturing onto the motorway.
The inability to make decent progress and the fear of breaking down knocked her confidence in motorway driving. She's better now, newer more powerful car, but if we're out together on a motorway it'll be me driving.
I would say that the general standard of driving across the board is falling not just on the motorways.
The test isn't really fit for purpose any more as others have said no motorway training, no skid control lessons, do you even have to drive in the dark ?
One test when you are 17 shouldn't be it until you have to reapply for a licence at 70. It's so easy to pick up bad habbits without realising, and I cringe when I'm out and I see the standard of driving of some of the more senior motorists out there. (My mum scares the living daylights out of me and unless unavoidable I don't let her take my kids out in the car)
Additionally how many drivers ( and I guess it's many of us on here) have had any training over and above DVLA test. Theres the pass plus schemes for new drivers, IAM for established motorists and I know that some companies send drivers on various schemes, but for the vast majority of us the DVLA test is the one any only assesment of our driving at all.
Then we have the multitude of drivers who learnt in a different country to different standards that are let loose on the roads for up to a year before they have to obtain a UK licence, but thats another discussion I guess.