Re Cinebar's point: "I don't have this problem at all. I am wondering how many people are culling townies and not leave the game a way to fill jobs other than the current households. Culling Sims in Manage Worlds should generate new Sims, correct? However, if your population is too low, wouldn't that mean the game has to use your own Sims to fill the jobs that need filled?"
I had it happen in a test game with 12 played Sims + 35 nonplayed housed Sims at the start of the game, and in which I did no culling at all (there were about 50 unhoused townies by the time I finished testing) and had no mods. I gave 10 of the 12 played Sims jobs myself at the outset and left the other 2 unemployed, and let the game hand out jobs as it liked to nonplayed Sims, both housed and unhoused. The game turned one of my unemployed played Sims into a Painter almost right away; I had no played Sims in that career, so no reason for the game to need a Painter. By the time I finished playing the test game, I still had at least 25 nonplayed Sims who didn't have assigned jobs ("at least" because I never got to find out all of them before I was done). So there was absolutely no requirement for the game to assign my played Sim a job, and not that job in particular.