I guess it works on a lot of levels because there's so much to do in the game. I don't know, for me, I enjoy mapping out how a Sims life will turn out whilst I'm still creatng him/her... I enjoy making up stories and because I'm not good enough to write a story book or something I can still make that stuff happen, without all the writing malarky
i think one of the reasons is because u can control everything that happens to the little dudes so you could protect them from all the horrible things that happen in our world and maybe wish to be in that world with such naivety
guiding them through life. u make whatever u want. plus, all those download sites. etc,etc.. reason=endless.