It is definitely labor. And the only unpaid work I've done in 20 years is for showreel, I definitely don't do unpaid theatre and haven't since I graduated drama school.

Learning lines (which is unpaid work before rehearsals even begin), blocking (and depending on role: combat, intimacy as is being discussed, music/song, choreography, props and costume tracks) are all pretty hard work. Not to mention 5 weeks of 10 hour days 6 days a week as a standard rehearsal process (all of which is usually done standing and moving, so generally harder physical work, longer hours and fewer days off than an office job).

To say nothing of "hell week" (tech and dress).

For us semi-pros, I'm often doing my day job around roles as well.