In a different thread Mikey Lewis points out there are far more agents for actors than for composers.
WHY IS THAT?
A glance at IMDB provides a clue.
Actors typically outnumber composers on a project by a landslide.
A film like BLACK PANTHER lists a cast of 145 actors vs one composer. A TV series like CSI: NY lists one composer and 2,350 actors during its run.
There are typically far fewer available employment slots to be filled by agents for composers than for actors.