It isn't an automatic excuse. I got to serve jury duty even though I'm a solo practice attorney. I had to close my practice for a week. My father- a solo physician- almost got picked for a murder trial that ultimately required a 36 day sequestration.
You have to prove that you're a sole/main provider of income or care for your household, primary guardian & caregiver for a minor child or disabled adult or the equivalent. Deployment by a superior sovereign - IOW, getting called up for your Army Reerve unit, going on a mission while on active duty, etc.- also gets you out.
You could also be a scientist.