Most of this makes sense if you're keeping the system fully powered on, but doesn't apply in sleep mode. Energy usage is a rounding error, there's no heat, it's not online, there's no r/w operations. Blackouts and lighting affecting sleep is a possibility, but I've reached a point of taping over anything that emits unecessary light.

The main benefit is that not all environments have a session manager, and I personally have a lot of programs open that I want to have instant access to and not have to spend time opening them and potentially creating a distraction during my wakeup routine.