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.

Does the AI actually do everything, or just act as the CEO?

It'll ultimately take a lot of time to produce a polished product that people actually want to use. We're seeing that clearly. The vibe-code-an-app-this-weekend capability is producing almost exclusively a giant pile of worthless garbage, rather than an explosion of apps that humans want to use. It's mostly someone in a garage welding two pieces of metal together for the first time, and then roaming the neighborhood in celebration: look, look at what I have done, look, two becomes one, I have done this, look, amazing, I could probably build an airplane or a generator.

The bar will be raised + it'll turn out to require a lot more time & effort than is currently thought to produce something of good quality (even with Fable 6 et al). The smaller utility programs are easy for AI to turn out.