Another little thought about football (soccer) tactics.
Having just one forward restricts too much the options of attacking tactics: he can only dribble and shoot. Adding another forward enables a lot more options (because they can pass the ball back and forth), so he has a great marginal value.
If there was no offside rule, having one or two players beyond all the opponent defenders, in front of the opponent goalkeeper, has some benefits (as well as some disadvantages!). But the marginal benefit of adding other players in that position is almost null.