Three structural reasons licensed trades are protected from automation.
Physical presence
Running conduit, soldering pipe, and diagnosing a tripped breaker require hands in a physical space. No remote execution. No software substitute.
State-issued liability
A licensed tradesperson signs off on work with their personal license number. That legal liability cannot be assigned to software. States require a human.
Regulated by law
Occupational licensing is codified in state statute. Changing who can legally perform this work requires legislation, not just better technology.