I would argue that most people don't make their own clothes mainly because the time and effort required to make clothes is VASTLY disproportionate to the time and effort required to buy clothes.
For food, it's the same. Learning to cook palatable meals from ingredients (anywhere on the preprocessed spectrum not just raw) requires a lot of learning and often new kitchen equipment.
Especially if you're truly starting from 0, as in no cooking knowledge was taught to you by family or community and you didn't inherit any equipment.
Why should we expect people to sacrifice the time, money, and energy that their job is demanding more and more of from them as time goes on? Is cooking really different from all the other domestic skills that are no longer expected to be known by at least one household member?
More importantly, if encouraging cooking really is a more efficient way to improve average nutrition, why are we so quick to scoff at people who don't know this skill, instead of acknowledging the myriad of reasons they were discouraged from acquiring it and using that knowledge to help us campaign more effectively?
(not saying you specifically were scoffing but def other people in this thread and people I've discussed this with IRL have, including myself in the past)