So I am writing a Sci-Fi novel where humans are currently spread out over 440 Star systems ( ~ 2000 Light years). There has been several breakthroughs in Automation technology and all manual labor jobs are done by bots. Humans are only needed to supervise and work in certain service industries (Therapy, Writing, Acting etc..)
So I am having a hard time justifying a large population. In fact, my calculations are currently giving me less than 1 billion people. What would people do in such a society? Does a large population even make sense? ( Large meaning in billions)
I thought about having a large military (Occasional conflicts with aliens) but even that would not require billions of humans.
PS: There is no FTL travel, Only FTL communications. There are Stargates (Discovered from ruins) which are used to go from system to system.
Edit: The people do not really need to work to survive. Agriculture is fully automated and can easily meet the demand. If a family is just trying to meet basic needs then one person probably only needs to work once a week ( One person in a 4 member family). Yet there are things like spaceships which are very expensive and would need decades of income for an average person (For the cheapest shuttle). Real estate varies by location. Real estate on a space station is vastly more expensive than a planet.