Not gonna lie... I'm part of the pre-ordering plague that is killing video games.
I usually pre-order a game maybe a week or two before its release, usually if the preview gameplay looks interesting enough, or if its from a game studio that I like and I want to show my support, especially if it's a middleware/niche titles like Earth Defense Force, Sniper Elite, and whatever Suda51 or Swery65 are creating. In special instances, like with Fallout 4, I pre-ordered that thing back in June so I could get the Pip-Boy Edition.
The only other justification excuse I have for preordering games is simply for the minute, three-minute thrill I get when I get something new in the mail. Where I'm located is rural as fuck, with the closest GameStop being about 120 miles away, and seven months out of the year it becomes the land of ice and darkness and therefore pointless to drive anywhere outside of town. So what I get to do for entertainment is limited: either I start doing meth, I start drinking, I start creeping around the high school sporting events, I start watching TV, or I pre-order vidya. I realize the sane, more prudent option would be to wait a few months and wait until the game's price goes down, but I assure you when you live this far out from civilization, I really don't mind throwing down an extra $20 to feel somewhat connected to anything besides Luke Bryan and the prices of canola seed.