The easy problems are solved. Crud with the preferred language and framework is a known quantity and can be "ok here we are and go" and you can get a boot camp or new grad and have them do that.

Let's say that we need to solve a new problem. The shop language is Scala. Who can learn how to program in Scala? Can the boot camp who learned how to do NodeJS be trained in Scala? If so, how long will it take? If we spend a year to get them to being an acceptable Scala dev, will they get a new job immediately? If we are paying a "we are training you low rates" can we get any applicants? If we are paying a "we assume you to be a skilled Scala dev in a year and we expect to get 2-3 years of productive work beyond training" rate and they leave immediately after getting them sufficiently trained... what then?

As many developers see themselves as a "Java developer" or "React front end developer" rather than a software engineer, the mismatch is akin to asking "why can't we get plumbers to do electrical work?" The people who are Java developers or React front end developers are skilled in the trade rather than as a knowledge worker in software engineering.