I now realized your talking about something else in comparison to my prior reply.
Seems like you've been looking at free charts offered by different data vendors.
Anyways, some futures trading instruments make very important price moves in the overnight data due to key market events.
In situations like that you definetly want to include the overnight data session info into any trade decisions you may have during regular trading hours.
Therefore, if there was not any important overnight price movement...
Ignore that particular trading session for that particular trading day especially if your a day trader.
However, if your a swing trader (holding trade positions overnight) or position trader (holding trade positions several weeks or more)...
You definetly want to include the overnight trading sessions in all your trade decisions to prevent missing critical price movements that have impact on your trades.