I think the "problem" with offsides is that it is a little too subjective (since the line moves with the players).

There are subjective things ... that player was offsides but "not involved" in the play (3 seconds in basketball assumes everyone in the paint is involved in the play. Football certainly assumes that everyone on the field at the snap is involved in the play ... even guys trying really hard to get off the field who clearly AREN'T involved in the play)

And since the line is moving with the defense, there are questions about "even with" the defense or not.