Why are there then no women who are professionally engaged in milk production and do not sell human milk in bottles?
The demand would be.

I answer as a "manufacturer", which has not so long ago interrupted the entire internet on this topic.
In general, human milk is on sale, but not at us. There are storage banks of breast milk, from there it is often purchased for experiments, some try to treat cancer, someone takes for their infants, etc. History also knows some local traditions of drinking crushed human milk for beauty-health-longevity. Only in an industrial way to stamp the mixture is easier and cheaper, and even cheaper milk from a cow or goat. Women have little power. Plus, it is not so interesting - to scratch from morning to night. They usually sacrifice or sell surpluses.
Although some don’t sell anything to anyone, but let it go into the pot or on blinkers. There was also news about ice cream from breast milk. But most people under such news write ‘fu’u’u’u’u’u, ‘buye’u’u’u, and ‘how can you eat it at all, it’s the same human discharge’, so the high cost and low productivity are not the only obstacles to selling breast milk in bottles.