I agree with @Nikkei_Simmer "That's life". It makes the game even more interesting and more "alive". It's not different from downloading sims that people have uploaded for sharing. Some people have my selfsim in their games.
Many populated CC worlds have sims the creators have played for a while, but sometimes they have used mods to give them skills and certain career levels, and things like that, so when you start playing in it it will be populated with sims that have a history. :)