Comment by kfse

That actually has a simple answer, for most businesses it's not that you can't do what your suppliers do for you, it's that you'd rather use your resources (time and capital) towards something else because that's where they generate the most value.

For a simple example, I know how to make sandwiches but if I'm throwing a customer event I just want to buy them from a catering company. Then they have to deal with buying ingredients, hiring people, doing health code inspections, getting liability insurance, etc. Even if an AI could do all the management of it for me, I still wouldn't want to put in the capital resources towards it.