omg, Igzigpuff, you sound like me.
Normally, I make my sims, they live forever, never aging, they live in an awesome beautifully decorated home and they have a ton of money in their banks so they never have to work this way they can stay home and just work on their skills. I don't know why but I like having all the possible skills maxed out. *shrugs* I'm weird I guess. So Legacy is a real challenge for me. I can't cheat with the money, my sims get old and die and I have to focus on many sims at once. Totally not how I used to play...but that's what I'm liking about it!
And I still remember my sim from the original Sims where I had her focused on working on her magic skills. That was a lot of fun. I was a bit sad when I had to uninstall it.
I think anything you spend a lot of time on, you will become attached to. And it doesn't help that like Pam mentioned, they are realistic and show emotion -and they DIE for pete's sake....and never come back! At least in WoW my character comes back after she dies...