It's the same reason that for 80 years after the invention of the commercial icemaker in 1842, the American ice-harvesting industry produced more frozen water than manufacturing plants. And the ice trade did not exist until 1806.

https://en.wikipedia.org/wiki/Ice_trade

It was more economical to send people out to cut ice from a lake in Maine and ship it by rail to Chicago than it was to just freeze water from a local supply. It was also more reliable since the technology was mature, versus ice plants that often broke down when meatpackers needed a consistent supply.

There's no reason why this won't be the case for AI unless semiconductor manufacturing continues its exponential performance/cost growth. The demand for technologically obsolete goods and services do not instantly disappear when a superior product enters the market.

Human software engineers right now are more reliable than AIs for most price-points. This is true for most industries in which machine learning is present.