Are teachers too influential to have them promote their subjects in K12?

This is a non-problem. If you believe it's a genuine problem, please show us some data which demonstrates that.

i never once had a teacher in K-12 tell their students "you should study for a job in Field X." i had a handful of teachers of who obviously loved the fields they were teaching (but not practicing) and that enthusiasm is certainly contagious to students who have an inherent interest in the field, but if a teenage student isn't interested in a field, they're not going to make a career path out of something a teacher of that field has said.

Note that i say teenager because in the K-5(ish) range, we all want to grow up to be fire(wo)men and astronauts and police(wo)men and doctors and unicorns. What a child that age "wants to be when they grow up" has very little, if any, bearing on what they will end up becoming. As far as time in K-12 school goes, only the later teenage years have any real influence on that eventual decision.

> As a result, they might pursue a career path that is not ideal for them.

Most people, i opine, do that just fine on their own without any prompting from their teachers.

PS for the non-US'ians: K-12 means "kindergarten thru 12th grade," i.e. the 13 school years most US'ians go through.

The curriculum that the typical American public school teacher teaches to is set in near–stone by the local school board and the local state education department. In turn that curriculum has to meet certain dates and targets for the myriad tests that students have to endure which are set by state and Federal education departments.

The notion that teachers have much flexibility to inject or promote their own subjects does not reflect the reality in most classrooms.

How do you teach something without “promoting” it?

Why do you see it as "promoting" vs "sharing interest and joy" in a subject?

What problems come from this?