It is only really in the last 10-20 years that scores have gone down - due to better playing.
In the past there were much higher scores.
Ultimately, why does the score matter at all? 1 point for 1 goal. Could make it 5 points if you really wanted.
Besides, the goal area is a lot smaller than it would be in American football. All you have to do is run over a line, across the width of the pitch. Here you have to kick the ball into an area a third of the pitch's width and about 2m high. Much harder. Not to mention the goalie.