Very few people like saved games. It's why no one downloads them. If a world is to be populated, players would prefer to have it be populated from the outset than to use someone else's save game because they like the idea of starting fresh. I know it doesn't seem to make sense but with a save game, people feel like they're getting a used copy of your world. And as awkward as it may seem, players may not necessarily have the same plans for your sims as you do. Creators will go through this effort creating all these elaborate scenarios for a specific family that they adore, not realizing that players may not even like those families and delete them as soon as they see them in-game, or have a completely different path they would like to lay out for them.
Why not just populate your world? It's not that hard, honestly, but people seem intimidated by the process. I wrote a tutorial here: http://www.thesimsdepot.com/sims-3/sims-3-help-center/create-a-world-master-class/caw-tips-and-tricks-populating-your-world-and-beyond/. I know it seems like one more step you'd rather not take, but it's better than using a save game, IMO.
