They seem to be thinking about it too deeply; Sims is like watching a TV show following a persons life, you want drama to happen, death, scandal; or you wouldn't be watching. It's also an opportunity to try things we never would in real life. I do think the anonymity and God-power have an effect, though.
Myself, I get attached to some of my sims, but the others I'd happily let die, or be tortured; sometimes I put the ones I like through hard times as well, but I know it will turn out good for them in the end. If anything, that's more psychological; that we can attach to some things, but consider other equal things unimportant and expendable.
