that's like baseball getting rid of their outfielders or football getting rid of offsides or basketball getting rid of traveling.
the sport originally DIDN'T have an offside rule. but it took away from the game because there'd be a player camping out at the goal area at all times waiting for a long ball to be passed to him. and, even then, he wouldn't always score because the keeper would be on him. they, eventually adopted the offside rule as the sport got bigger and in 1990 or so fifa decided to change the old rule (where anyone past the last defender would be called offside if the ball was played forward whether or not they were the intended receiver) to be more offensive attack friendly to allow for more chances to score. then, about 4 or 5 years ago, they tweaked the rule again to make it better for attackers.