Rodgers should be the #1 QB pick (its either him or Brady usually). But drafting a QB early in the first round (other than prime age Peyton Manning, Rodgers in 2011 or 2007 Brady with Moss) is a big opportunity cost.

Most leagues have 10 or 12 teams. Each of those teams needs 1 QB. There are 32 of those guys available, not all of whom will start every game but most of whom will throw a large volume of passes. The way that QBs are scored (esp. 4 points per TD, 1 or 2 points deducted for TO) means that the gap between the top QBs (Rodgers/Brees/Brady) and the bottom (I won or nearly won a fantasy league with Blake Bortles' garbage time extravaganza) isn't that huge a number.

Tradition and current league setup dictates your team will have 2 RBs and 2 or 3 WRs. There aren't enough top end backs to give each team two, nor enough top end WRs to get each team to three. For those positions, there aren't reliable difference makers by Round 4 and you are hopeful to get someone reliable without much risk. To get top production from RB or WR after Round 3, you need to draft some risks. In most drafts you can get Rodgers or Brady early in 3 and Ben or Brees in the fourth. In a Wisconsin league Rodgers is probably gone earlier.

The most logical way to deal with this is a league that requires you to start 2 QBs each week. Then the shit hits the playing time fan. Most players hate that setup for that very reason. 6 points for QB TDs and bigger deductions for turnovers (QB always lead the league in TOs) is a way to make the difference between the top QB and the 12th QB wider.

Rewards teams that invest in a QB earlier.