Cooking is the same thing. I could almost certainly earn an extra $15 each night driving Uber for an hour, instead of going home to my family. The fact that I don't do that puts a lower bound of $15 on how much I value that hour. If I'm forced to do some chore during that hour instead, like cooking or cleaning dishes, you have to account for the $15 in lost value of free time.
I think the hard part is that cooking and cleaning (some items) can be done while effectively multi-tasking, chatting about someone's day or collecting one's thoughts. I have a young daughter and when I put something in the microwave, cut up vegetables, fetch spices, or load the dishwasher, we can generally keep the conversation and activity going. Cooking or baking something from scratch is obviously much more time-intensive. Getting food delivered doesn't really save that much time. However, cleaning the bathroom or vacuuming are generally blocking activities and thus easier to rationalize outsourcing. I would agree that we as humans have a very hard time valuing our present and future time, so I would always love to have sometime critique my day. "Hey, you enjoy your job at tech company X enough for the next two years, so it seems like you can afford a laundry service for the next 10 years, time which you can spend more at playgrounds and working out, why don't you do it?"
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.