What's something about football/the NFL that took you WAY too long to realize?

Not sure if this is the subreddit for this but I don't know a more fitting one than NFLNoobs.

For the more experienced guys in here, or some newer noobs still learning new things, what was something you didn't understand about the game for the LONGEST time, to the point where you felt dumb for not realizing it sooner?

I'll go first, because I have two:

  1. I didn't understand for an embarrassing amount of time that the reason playcallers run it on 3rd & long (think like 3rd and 24) isn't because they're stupid enough to think their RB could make it the whole way for a first down, but because they're essentially "giving up" on the drive, and getting ready for better punting position that they couldn't get from an incomplete passing play.

  2. I thought it was "receiving core" for the longest time, didn't realize until a while ago that it's "receiving corps". I thought it was "core" as in your WR1, 2 & 3 are the "core" of your team's receivers.

Does anyone else have something like this?