Why Backroll?

Hi all, im not sure why people backroll after spraying a surface. I can understand if the product is thick - like an Elastomeric product - and you want to roll out any air bubbles and make sure all the nooks and crannies are covered and filled.

But I have heard both sides that for regular painting - like Superpaint (for example), on a smooth or vinyl (for example) repaint of an exterior (for example).

I just wanted to know if you do or dont and why....

thanks for shedding light on this!