Remember in high school when your coach would make a challenge with one player to do something. If that person completed the task, then practice would end early. If not, it went on longer or there was a punishment like some extra sprints.
Needless to say, there was a lot of pressure on that player.
Placekickers feel that pressure almost every time they step onto the field. They feel like they have to make the field goal or it would ruin the game, no matter if it was in the middle of the first quarter or there were three seconds left in the game.