When peering into a dark house from outside, you often get right up to the window and cup your hands around the side of your head. why?

To remove the glare and shadow off of the window, this allows your eyes to adjust and focus easier in the darkness.

Hello :)

You often to do this see better to peak inside. See, by cupping your hands your shielding the glass from the light, which often creates the glare that makes it difficult to see inside.