Back in the 1800s there were to many goals scored. People were "loitering" by the posts. That is why the offside rule was implemented. Football (soccer) is a highly tactical game. It's all about formations and strategy (in addition to each player's creative outbursts).
I know the offside rule and its the worst in any sport. In hockey you can have a offensive player play behind the defensive to get a pass just as long as he is behind the offensive zone line (Blue line)... In soccer you need to play by the defenders! How the hell are you suppose to get a break away dribbling the ball? Oh... you have to wait for the ball to pass the defenders. Posh! Oh... and tactical? LOL tactical my ass... My favorite sports go like this. Hockey/Baseball then a distance away football/basketball... I actually dont like either one of those but the most tactical sport is Football... then hockey. Basket ball and soccer try to be but just end up being a clutter fuck.