Because they only know how to program with a framework. Take off the training wheels and learn the language and libraries.
Programmers comfortable writing in PHP and Go with their comprehensive standard libraries can also work with frameworks if necessary, but those who can’t get stuck as Laravel developers, baffled by the much larger number of projects and existing code that doesn’t use their “correct tooling.”
Programmers make claims about productivity and throw the word around, like we all understand what it means.