I am quite a good cook - so is my sister. BUT we were brought up with 2 parents who could cook and also had the time to let us help out and learn from them.
My 2 closest friends were brought up in a single parent family, by mums who worked several jobs to keep their heads above water and had barely enough time to sleep, let alone teach their kids to cook. Neither of them can cook very well, yet both are teaching themselves.
My MIL is a fantastic cook, yet dp until recently could not cook himself, not through her lack of trying but through his unwillingless to learn.
At school we had people in lessons who could not even boil an egg or make toast - they had never been taught, and school taught us little more than how to make pizza from ready made ingrediants (most of work was on food industry and things like packaging).
Living in shared households those that could cook (even basic foods from scratch) were heavily outnumbered by those who weren't sure even how an oven worked - but these people also didn't know how to budget or work a washing machine, or look after themselves in general.
These experiences aren't exactly in the minority.
Add to this the fact that I think we are rated 3rd in the WORLD for the amount of hours worked on average.
TV food shows and celebrity chefs are more food porn than cooking.
SO I think it comes down to a large amount of people in this country not knowing how to cook combined with a culture that works incrediably long hours and says 'want to make things easier - get a ready meal/sauce in jar' and the marketing that tells us these things are as good as homemade but without the effort.