The blues are very important but your numbers are off. You don't get any points for picking up blues. Just deny the points to the enemy. Therefore each one is just denying 2 points to the enemy. Red pickups net a point to the person who grabbed it and a point who got the kill at the time of pickup so each one is worth +2. From that, picking up a blue and denying 2 points to the enemy is equally important to the team as picking up a red and gaining 2. Not more important. You won't progress the game picking up just blues but it does have the same effect on the spread between the competing teams.