"_____'s Spirit is Fading Away" Message. What is this?

I use to hate the ghosts in Sims 2 mainly because I was concerned that they would scare my sims to death. In Sims 3 sims that weren’t living on the active lot would end up in the mausoleum when they died meaning if you wanted acces to their tombstone you could. I’m not bothered with this update considering that I have no interest in playing with the ghosts in Sims 4 as they seem to be pretty limited to what they can do unlike the sims 3 where you could make ghost sims and then have sim babies.