Some food I cook has to be prepared fresh. This becomes a last mile problem, where to have someone else do it they must either already be in my home or travel to it when I want food. There is still a travel problem if we instead say that I have to go somewhere else to eat.
I do cook some food ahead of time (lunch, for example) which would be more feasible. But I still have some problems with this. One of which is customization -- allergies, food preferences etc are numerous and present infinite combinations. That kind of customization eats into economies of scale rapidly.
Freshness is still a problem here -- say you can make food for the next week ahead, but that still basically means the travel/shipping time from the point of 'manufacture' is limited to a few hours at best if refrigerated.
Another problem is it becomes much harder for me to verify what was put in the food. There are strong incentives for a third party to put preservatives, sugar and salt, or cheap substitute ingredients that I don't want. You can work to regulate something like that, but it's expensive to police products with such a short life span.
Maybe no one has tried hard enough to solve this yet, or there are big cultural obstacles, but I'm not convinced that there really are economies of scale here, even if you account for unpaid labour.
These are real economic costs to outsourcing food making. I would love to outsource it, but there just isn't a cost effective way of doing it. I suspect that if the economies of scale here were real someone would already be doing it on a large scale and making a lot of money.