...but if you're evil like Carl and Willie, the moment you die, the Grim Reaper-looking spectres will come and drag you to Hell as soon as possible.
Makes sense.
The idea was that people who suddenly die (or die in general) but believe they have unfinished business or don't feel ready to move on, which was the case with Sam, they stay on Earth. Evil people who die become hellbound or, continue to live on in spirit form as a punishment, or refuses to go until Satan comes for them (they stay in Limbo).
Sometimes, places were evil is committed attracts demons after the person goes to hell.
These are my views. But as for your question, hopefully, my first sentence answered it for you.
Good dead people with unfinished business can hang around.
Bad people go straight to hell.