Having followed facebook's platform and interface changes, there were a ton of do-overs, removing features than adding them back then removing again. It's more of a "move fast, break things, then fix it again" trial-and-error attitude. The friends list thing was an afterthought and always remained as such. Plus it is difficult to enforce them now, as people have adapted to having a single friend list, while G+ enforces it from the start.

I find google circles a very engaging idea, as your friends list will never get stale. Total sharing may be less, but you are no longer afraid to share (e.g.) technical stuff with your colleagues. The problem is how they're going to figure out re-sharing right.