How come there is no union for theater administrative workers?

Actors and stage workers have Equity, but those who work in the Box Office and other administrative offices do not have a union. Why is that?

How come there is no union for theater administrative workers?performing arts center

They don't need them.Equity (and Sag and all the others) are in place to ensure safe working conditions for the actors as well as provide benefits like healthcare. Because actors, stage managers, etc can work for any theatre, it doesn't have to be the same one (unless you have a contract that states that, though I've never heard of it), they're more like independant consultants who are employed by the theatre for the duration of the rehearsal period and the run, that's it. They're not "full time".

Full time admin employee's of a theatre will usually have these things covered by their employer, which is the theatre. There are already laws in place regarding overtime, etc for these kinds of employees.

It's apples and oranges.

How come there is no union for theater administrative workers?sunshine opera theater

Its better that way.
If one doesn't exist then you should start one! I know people fear being the first to do anything. They will join an existing organization, but rarely want to start one...Perhaps the interest is there and you may be the spark to get this going... Give it a go mate!