Pressure is derived from stakes. The more you have at stake, the more pressure you are under; the more you have to lose, the more you need to win.
Because of the way we talk about football, quarterbacks are almost always under more pressure than their counterparts at other positions. They are the ones whose legacies are tainted by the stain of non-accomplishment, who live with the burden of never having won "the big one" during college.
I'll give you an example. Adrian Peterson was one of the best running backs in college football history. His numbers are deflated because he only played three years and suffered a couple of injuries, but when he was on the field, there was almost nothing like him.
Because he played running back, though, we tend to forget that he was 0-2 in BCS bowl games, losing the national championship game by 36 points to USC as a freshman and the Fiesta Bowl against Boise State as a junior. But no one brings any of that up, and when he got to the NFL—where he has still yet to win anything of import—Peterson was not labeled someone with a monkey on his back.
Compare this with how we talk about Peyton Manning. He always came up short in college, and if not for his one Super Bowl with the Indianapolis Colts, he would still be regarded among the greatest losers of all-time, alongside other quarterbacks such as Dan Marino.
Which is to say: There's a reason this list skews toward quarterbacks. They do not make up the entire list, but they make up most of the list, and they do so with purpose.
In some cases, they need to justify their old recruiting ranking. In others, they already have by putting up big stats...but now only winning will ensure their name gets remembered fondly.
The pressure has been cranked up to 10.